I stayed in one in the Lakes in October and it was great, proper cosy and the one I stayed in did have a heater. They are an excellent alternative when the weather is more inclined towards inclement. You do need to take all your other camping equipment though.
I'm 6'4" and just found that it was a little to close to head and feet to be comfortable. I could have lived with it but when you are spending that sort of money on a tent you have to consider whether you are happy making that sort of compromise.