I would like some apple tree pruning advice please

As above, with a Jonagold apple

I think you need to remove the leader back to the topmost branch with the aim of promoting 3-4 strong laterals for subsequent pruning next year. But I would wait for FB to respond as he is the fruit tree expert and I would defer to him.

The pruning depends on the rootstock ... does it say on the label?

The Bramley looks like a "leg" tree, a style which is popular on the Continent. If so it probably doesn't need any pruning but will need a 6ft stake to support it.

What's the rootstock?

Assuming the rootstock is suitable for half-standards (by which you mean a trunk of 4-5ft), I would:

Bramley:
No pruning; it should send out some branches in the several inches below the tip of the leader, so it should naturally create a trunk of just over 4ft (half-standard).
In later years, the lower side shoots can be removed if they are not wanted. If you leave the lower shoots unpruned they will fruit in 2015 while the top of the tree continues to grow - assuming the rootstock and soil are suitable.

Jonagold:
Cut back all the long straggly branches and the leader. Remove more than one-third but less than one-half of their length.
I can't tell for sure from the pictures but you might have twin leading shoots on the Jonagold. One of the two competing leaders (A or B) might need to be completely removed to prevent the tree splitting down the middle in several years time.

No mention of rootstocks, but each label says final height 1.5 - 3.0m (6 - 10 ft)


The very end bud of the leader looks damaged, so I no doubt have to remove some of it, just don't want to remove too much

Yes, there are two almost identical leaders, one just a few inches shorter than the other.

I'm fairly certain this is a Dutch "leg" or "knip boom" tree on M9. It will not become a half-standard.

1.5-3m sounds like dwarf or semi-dwarf rootstock, as Orangepippin is suspecting.

The size guides on your trees are consistent with the dwarf and semi-dwarf size guide for M9-M26 from Keepers Nursery:
Keepers Nursery

Same size guide from orangepippin trees (he's probably not allowed to post a link to his site):
Fruit tree rootstocks and tree sizes

As it says on both website size guides: they will only reach the larger end of their size range if intensively managed - grown in good soil, fed, watered, sprayed and with a bare soil circle as far as the branches spread outwards to keep other plants (including grass) from starving them.
Without intensive management they will be at the small end of expectations, although the two scions (Bramley and Jonagold) are quite strong-growing and will probably result in a bit of a size boost towards the middle of the range if not intensively managed and perhaps a little bigger than the top end of the range if intensively managed.
Of course, that's assuming our guess on the rootstock is correct, and that it wasn't mislabelled in the nursery.

The minimum for a half standard with only minimal care (not much spraying, not much watering, competing plants, weeds or grass nearby) is normally MM106* and even that is not enough in the drier parts of Britain such as many areas in East Anglia, where MM111 and M25 are required to make half-standard trees.

* M116 appears to be an up-and-coming rootstock which makes an MM106-size tree without the disease or soil-fussiness problems of MM106.

OOPS!

I had a James Grieve in a similar style, and thought it was just cheap because the nursery hadn't tidied it up. I grabbed my secateurs and went all Edward Scissor hands on it ... Never heard of leg tree before. Lopped off the top, dipped it in root compound and thrust it into some fresh seed compost, cut it back to four main offshoots ...... if anyone want's me I'll be on the naughty step ....

Having just remembered the opening post said this:

It might not be such a bad thing that the trees may be on rootstocks more suited to bushes and trained forms.

I thought most allotments object to "trees", especially the shade they can cast over other plots and the wandering roots.

Sometimes a tree on medium vigour or vigorous rootstock will grow to look like that in its second year if it didn't have good weather in its first year or two and wasn't topped in its first year.

The picture below was taken a few years ago - it is a maiden M25 tree of a vigorous triploid variety. Sometimes, in good years the maiden triploids or other very vigorous varieties are so full of enthusiasm that they can't vent out all their energy into a single shoot, so they branch out all over the place.

-

I am really hoping that's the case. It looked (to my untrained eyes) like an uncut two year tree, which is why I got stuck in. However with it being an Aldi purchase, I'm wondering if it might be from the continent rather than the UK ... time will tell