I finally had to take mine down because it was blocking the entrance to my flat. Oh, well, too dark to study in there anyway!
There are a lot of options of where to get them...I'll fwd you a thread from a glasto site that has a lot of ideas. I got mine at millets for 29 pounds. There is a millets.co.uk site, but the tent i got was on sale and the sale was ONLY at the store, not online. I think it used to be on sale online, but they are all out, so it's just at stores now. There are a lot of decently priced options though - check your mail.