In reply to simon1985:
Bought mine from Taunton leisure- they had a tent show just off the m5 and we were going past. They were very helpful. If I was buying now, I'd probably get it from pro adventure in Llangollen, as it's my current favourite outdoor shop. I didn't bother with an inner, they are pretty midge proof, but a groundsheet is definitely worth it.
Thinking about it, proadventure have tentipi gathering weekends with tentipi cultists, where you can hire one and try it for a weekend. I've had a look and they've got one in a fortnight near Corwen. Might go myself
If you can find it, have a look at the blog of Tim Gent. He does a lot of canoe camping with tentipi stuff, but I think he might be sponsored. By them