Thanks for your replies.
Hmm, they may not actually be 25ft high, but definitely 20 and slender trunks.
I really do want to totally reduce the height of the trees rather than just prune them. I think I will try to go for the 5/6 foot level, if I can find a bud point (I just looked that up) and train the new growth out sideways.
And I may even get rid of two or three completely as the summer growth of the 5 trees overhangs both of my neighbours on both sides and those at the back too. Though they all had lots of fruit, as did a friend across the road.
I'll cut the trunks off at an angle, so that rain runs off, and coat the cuts with this special sealer from the garden centre.
Do you reckon I could splice healthy growth into the trunk? Just a thought really. Is there a season for that too? I just read "Prune in June" somewhere. And yes, I had heard about the silverleaf thingy from someone last year when I mentioned cutting them back.