Hi Lee, what sort of price range are you looking at? I've used quite a few with DofE groups and there are options ranging £70 at the cheaper end to £200+
At the moment we're using these for the cheap option http://www.cotswoldoutdoor.com/index...up/857/level/3 but also have some of these http://www.cotswoldoutdoor.com/index...up/857/level/3 for silver expeds, not quite as big but much nicer. Also depends on how much kit they're carrying, do they need a decent vestibule. If you've got more cash the wild country tents are good. I'm currently using an MSR Carbon Reflex 3 which would make an ideal group tent, easily enough space for 3 and 2 large porches to allow you to get out of either end.
Give us an idea of price and number of tents you're after and I'll try and help out a bit more
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