Thanks very much for your help and the link Suewick! I went last week and now think Manchester is a great city.
We stayed in the Premier Apartments not 5 minutes walk from the Arndale centre and they were superb. Unfortunately I didn't have enough time to make it to the Trafford centre, but for shopping everything you could want is already in the Arndale and around the Triangle area.
We ate in Old Orleans (nice, but average), Cafe Rouge (enjoyed the chicken in leek & white wine sauce dish) and the Living Room (I particularly recommend the chicken, bacon and mushroom pie - I'm still dreaming about it!).
It did feel like a rushed visit so will definitely be returning for a long weekend to catch up on everything we missed out on like Canal Street, Harvey Nicks and Chinatown.