Was poking around on Virgin Mobiles website and they seem to have a few good deals especially if you use a lot of mins - at £15.99 and £25.99 I think its pretty competitive too. They are just for current Virgin Media customers and I've listed a few of the deals below:
HTC Wildfire S, 1075 Mins, 3000 Virgin to Virgin Mins, 250 Txts and 500MB Internet for £15.99/month = £383.76 over 24 months
HTC Sensation, 1125 Mins, 3000 Virgin to Virgin Mins, 5000 Txts and 1GB Internet for £25.99/month = £623.76 over 24 months
Add £7.99 for delivery - steep, but hey. Hope these are of use to some.
Also please leave a comment if voting cold, cheers.