Well, what are you looking for in the phone? my specification was maximum 4inch display, if Android minimum 1GB ram. Otherwise I did not care for operating system.
Al go to phones for u. They did me a proper good deal which bought me out of my contract with 9 months to go and gave me nearly £200 off of a new phone.
Virgin on obviously will tell you it costs a fortune for you to buy out of your contract to keep you there. But other companies will actually buy you out of your contract for switching and going with them. That's what Sub is getting at.
But if you're looking for a certain phone, I would maybe take some suggestions off the other thread, go to a phone shop, or buy an iPhone.
I am not in UK so cannot advise on deals like that.
Personally I would not go bellow 1GB ram on the phone (main problem on existing small Android phones). As your previous phone was 3.5inch display phone, something between 4.5 to 5inch may be good transitional phone, unless you want to jump to something even bigger, which may be bit of a shock.
I guess the main question would be how much you are willing to spend.
I got a second hand phone from friend, and I know he treats his electronics much better than I do. So the phone is in almost pristine shape. Personally if you buying second hand, I would advse to see the phone before paying. I guess easier in my home country as its very small and its easy to travel to a nearby town relatively cheap to check the phone before you buy it.