Just looked them up - FOP Gimmy does look good and would fit. Not bad price either - found it for £28.69 with £3.75 postage.
I couldn't resist I put in a bid on the Cambridge on eBay
I do like that cage, there were some at the rescue I worked at, and they seemed very spacious.
I think I'm just being a silly-hamster-mummy about this. I think if Phoebs was a smaller hamster I wouldn't feel so bad.