Eccles
It's definitely the case that different mobiles are capable of operating at different signal strengths. It can even come down to how you hold the phone, as demonstrated by Apple's iPhone 4 debacle:
http://news.bbc.co.uk...echnology/8761240.stm
It seems you are not the only one with this problem however:
http://www.htcwildfir...ing/signal-reception/
That said, a colleague had trouble getting a signal on a new Blackberry, coincidentally after upgrading from a Nokia E63. In the end he replaced it for an identical model that worked perfectly, i.e. it can even come down to the individual handset you have, not just the handset model. Or maybe there was a genuine fault with his handset, even though it worked OK in other places.
So you could ask for a swap and hope you get a better handset, or you could send it back and return to your old handset or a different one ...