Of the 14-15 species of bat resident in UK all but two are myotid (i.e. they hide away in cracks & crevices so you would be very lucky indeed to see them on a "normal" caving trip). The remaining two which you see hanging around in caves are Lesser and Greater Horseshoe bats (both of which are endangered species and the colonies tend to be located in SW England and W Wales & W Ireland). In general bats presumably will tend to live where the weather is conducive to there being a plentiful supply of food (insects) and also where the weather is temperate - they're warm-blooded beasties, after all!
Of course all cavers acknowledge and respect the legislation protecting bats in this country and it is worthwhile pointing out to any potential new caver that the bats are probably more scared of us than we are of them (even if this isn't true it should help calm their nerves) and that bats' echolocation is so excellent that they'll fly straight past you without you probably even knowing about it.
I'm not sure if I can remember the UK resident species but I reckon they are: Brandt's, Daubenton's, Whiskered, Pipistrelle, Greater Horseshoe, Lesser Horseshoe, Barbastelle, Grey Long Eared, Brown Long Eared, Liesler's, Noctule, Serotine, Bechstein's, Natterer's (the Mouse-eared bat was considered extinct in the UK but I read a report this year which suggests they have been rediscovered here).
The lesser horseshoe bats which are commonly seen in caves in Mendip and S Wales are usually referred to as "cute" by most newbie cavers I've been with (especially if you tell them that they only weigh in at about 5+g - or the weight of a two pence piece).
I also recall reading somewhere that bats live for up to 30 years and hibernate once they have become pregnant/storing sperm (which is why you shouldn't disturb them whilst hibernating since they "abort" the sperm they are carrying) - apparently they only have one kid at a time and so it's important to maintain the gene pool by not upsetting any colonies. Greater horseshoe bat colonies are not uncommon on Mendip (but the locations are guarded) and they are quite an impressive size - up to 35g in weight with a 40cm wingspan).
Any bat specialists out there in caver-land who can add further to my limited understanding on this topic?