That's a worthwhile thought, Dove. The first owner of this garden had 4 espalier apple trees growing down the centre; only two are left and they're not exactly trained now. Concorde is one that I like but Doyenne du Comice is my absolute favourite so I'll have to check out pollinators.
I may well do that Dove, our allotment is a new plot so we can pretty much do what we want with the majority of it (setting it out). We need to have some trees towards the back so we can grow things in the ground beneath that don't particularly like full sun (blueberries, rhubarb etc). The birds are the biggest pest there so we're going to need to put netting up.
Flo as a general rule with fruit I've found having more than one of each gives better results individually, I'm not yet sure on cross pollination so I'm probably not the best person to ask. My garden at home is small and packed with plants already so if it wasn't for the allotment I wouldn't be able to even consider growing any more fruit trees.
Flo, I always understood that the best pollinator for Comice is in fact Concorde. I have both but the Comice still remains a bit of a failure each year with only a couple of pears. I think it doesn't like my sticky clay soil and would much rather have a chalky or sandy bed for its roots.
Regarding gages, yes they are a great fruit with rich spicy aroma. Better than the best of plums, so it surprises me that I've never planted one or two of my own. My mother-in-law's Old English variety is lovely but I can't say which is the frontrunner for flavour, hardiness, reliability etc.