Victoria plum trees

You are likely to have a poor crop following a heavy crop, yes. In heavy years, you should thin out really well to improve the crop for the following year

As to pests - you really need to know what it was for us to suggest a remedy. What were the symptoms? Many of us on here don't go down the chemical route unless as a last resort

Plums can be bienial. Some varieties worse than others.
Almost any type of fruit tree will turn biennial if not pruned properly and regularly.
A plus point about biennial bearing is that the maggots that may tunnel into the fruit are badly affected by lack of food supply in the "off" years.
The smaller fruits often found on biennial trees are also less attractive to pests.
An abundance of pests can be beneficial; naturally thinning the crop.

I've never had much problem with plum pests (I had a Victoria), but I'd say that fruit-tunneling pests - such as plum sawfly - will need preventive measures from around petal fall, to a few weeks after the petals have dropped. The pests can be flying-in from other people's trees.

I'm against using chemicals, so I either:
1.
Tolerate a few damaged fruits.
2.
Use the tree as a "companion planting", to draw attention from my other trees.
3.
Remove the tree and grow something less troubled by pests/diseases.

Since the plum variety "Victoria" has been so widely grown for so long, there are now many pests and diseases evolved to attack it very effectively. Victoria is now regarded as being very susceptible to most plum problems.

Would "sacrificial crop" be what you intend? Like I grow nasturtiums to draw the blackfly and cabbage whites away from my brassicas

Yes. I find that some varieties are excellent "sacrificial" crops.
As you know: my main interest is apples - because growing conditions are difficult and apples are more tolerant and more diverse in their tolerances of conditions.

Discovery, Ellison's Orange and Scrumptious apples bear the brunt of maggot and pest attacks, while the remainder are virtually pest-free.
However, in years of poor pollination, there aren't enough Discovery, Ellison's or Scrumptious to go around, so the pests start to turn their attention towards the usually-more-resistant types.

Likewise: my Bountiful, Meridian (both Cox's offspring) and Bramley are very attractive to the woolly aphids (a very serious and disfiguring pest in mild/dry climates). My other apples are much less affected by woolly aphid as a result of these decoys. Unfortunately, the decoys need regular reconstructive pruning to remove the split and twisted branches caused by the woolly aphids.

Is there an alternative variety that is similar to Victoria in taste/appearance, but less susceptible to pests and diseases?

(in a similar way to how you might grow Tydeman's Late Orange instead of Cox)

Plums aren't easy to grow in this area, due to low rainfall and light/shallow soil. Plums need a good moisture-retentive soil.
The trees fail to thrive in poorer/dry soils - they are very reluctant to grow roots in such poor/dry soil as is found in or near Cambridge.

The fruits often grow only slowly in this area (and rarely become large-sized). If we get a spell of heavy rain, the fruits then try to "catch up", but grow too fast in their hunger for water, and subsequently split and rot.

As a result, I abandoned plums and I would not recommend them close to Cambridge. Pears too.
I dug-out my last plum tree a few months ago and it went to a new owner in Cambourne, where the soil is better.
It was a Victoria (St.J.A rootstock).
It was planted in my best spot and I did all I could to make it grow.
It managed a pathetic 5ft height/spread in ten years despite my best efforts, whereas it should have reached twice that "according to the book".

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I can't offer any suggestions for a good plum tree for this area.
However, I would recommend that you take a good look at your soil:

Depth of topsoil.
(ideally needs to be 2-3ft; I have 1ft).

The subsoil (I have fast-draining gravel that quickly drains away moisture, as do many parts of North Cambridge. Other parts - South and West of Cambridge - have impenetrable chalk).

Quality of topsoil.
A well-balanced loam, with equal amounts of sand, clay and organic material. Much of Cambridge is loamy sand, or loamy chalk.

The flat lay of the land and persistent breeze is very drying to the soil (hence all the windmills to the North and East).

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If I ever tried to grow plums again, I'd go for the absolute strongest rootstocks that I could find (such as Brompton). They would probably reach about half the "expected" size and make a nice bush - around 10-12ft.

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I started with apples on M26/MM106, pears on Quince A and plums on St.Julien A. The intention was small half-standard/large bush trees, around 10ft (3 metres). Only the odd one has exceeded 6ft. Most grow only 4-6 inches per year, no matter how hard I try. Poor root growth predisposes them to other diseases.
Nowadays, I am using a mixture of "very vigorous" MM111, M25, Pyrus and seedling rootstocks, to attain 10ft/3m trees. They grow about 1ft per year when young.

It is far easier to reduce the vigour of a strong-growing tree than it is to increase the vigour of a weak tree. I plan to grow a cordon on "very vigorous" M25 rootstock, to prove a point.

I really urge you to investigate your soil, before potentially falling into the same pitfalls that cost me many years of blood, sweat and tears. I originally went "by the book", which did not apply to this unusual area.

;There's always another option Peachless. When you get your crop this year, make a note of what problems you get, then buy the appropriate remedy. I have a shed full of chemicals and use them at the appropriate time. I grow crops for me to eat, not the bugs and diseases.

The most effective, safe, all-rounder I use is SB Plant Invigorator. Every week if you have a persistent problem then once a fortnight to keep the trees clean.

looking at the msds of that product, i would never spray a fruit tree with it that often,looking on the site msds for the product,i t contains urea , urea can be a good nitrogen fertiliser sprayed at the right time, but sprayed that often it may/will effect fruit quality and i would imagine that it would reduce the flowering as the high level of nitrogen based fertiliser would make the plant grow leaves and stems not fruit buds/flowers

And the large amount of new growth would attract lots of insects to the plant, increasing problems with insects such as aphids

If you need to spray all the time, you would be better using one based on limonene as it is not a fertiliser , yet kills everything in site on contact but doesnt last to kill insects afterwards

its usualy better to ignore the insects and just wait for the predators to move in, or maybe buy some predators to release