I set up training quite a bit, so far have tried to use corporate style venues.
did a course at Durham Cricket Ground (that was fab, negotiated like mad and paid about £100 for the day)
Sport Centres are good (charge about £80)
Hotels sometimes have a corporate room (£120)
Try Bannatynes.
community centres are actually getting more up market, If you go to a newish one, they can be very corporate looking (£100)
have even hired a college, therapy room and class room (can't remember how much tho).
What I look for in a venue is parking, accessibility, is their eating facilities or nearby ones.