Conference pear rootstock

Quince C would be best as it produces a smaller tree. See this page Royal Horticultural Society | Advice Search | Rootstocks for fruit
The rootstock has no effect on pollination.

Climate, soil quality, water and pests/diseases vary enormously across the UK, so it's difficult to advise other people on ideal rootstocks.

Many of the "textbook" recommendations on rootstock choice are for trees that will be grown on deep, good, moist soils, with trees that are sprayed to protect against pests and diseases (which take their toll on the tree's strength).

Since my trees are not sprayed (I hate the idea of using chemicals) my trees lose quite a bit of vigour to aphids (suck the energy-containing sap), caterpillars (eat the light-gathering leaves) and the like, plus they lose some vigour to various disease attacks (scab damage to leaves, canker damage to stems - in wet seasons).

Personally, I go for slightly more vigorous rootstock and then prune in July to control vigour (if necessary), rather than go for slightly less vigorous and have a tree that always needs lots of feeding, weeding and attention. I like my trees to have a little extra strength, to be able to survive a little neglect, harsh conditions, or recover quickly from breakage of branches due to accidents, storms or vandalism.

Using summer pruning, I even manage to maintain some "own root" Cosford Hazels to 6ft size (Cosford is an extremely vigorous grower, and is capable of 3ft of growth per year, with no feeding or watering, in my very poor soil - it'd probably manage several feet growth per year on an ideal soil!).

In my area, the soil is pitiful; low in nutrients which easily wash out of the shallow, dry- and-fast-draining (sand/gravel subsoil).
In this climate, Quince rootstocks cannot even survive, let alone grow.
I can only manage to grow my pears (on quince A rootstock) with their roots in the total shade of a fence and with grass over the top to retain soil mosture, but even then, considerable supplemental watering and some feeding is needed throughout the summer. My Victoria plum, on rootstock St.Julien A is the same as the pears; "theoretically" capable of 15ft, but, like the pears, has only managed about 5-6ft in ten years - with barely any pruning required.
Apple rootstock M26 is much the same as the above in my soil (very slow growing, very little pruning needed). In my soil, M27 and M9 simply die without constant attention.
MM106 just about manages to survive as a small, slow-growing bush without feeding or watering - especially when under the (vigour-reducing) attack of aphids/pests and diseases.

So, to the point; I suggest that organic growers should go for a moderately stronger rootstock to compensate for damage/disease/neglect. If it grows too fast, either reduce feeding/watering, or carry out hard pruning of the new green shoots each July.
Non-organic (feed-water-and-spray-people) should go for the weaker rootstock because food and water will be plentiful and pests not an issue.

thank you thats very helpful from both of you, will probably choose a C

cheers
Sarah

Excellent reply on rootstocks - takes away some of the mystery. Many thanks FB