i will be getting new ones from
Imac Fantasy Deluxe Hamster Cage 58x38x38cm - Berriewood Pet Supplies
they also sell the extensions too
thats one of the best prices i have found, and they have exelent service i have heard, they courier it to your door for about £5 (even with the extra tier its £5, so it works out good)
i am hunting them on ebay too, if they are local or have delivery, as i cant drive, and cant make my dad go half way across london for one XD
the cage she is in atm sounds ok for now, if you can get the fantasy that would be awesome! i am becoming a big fan of them myself haha