Thanks.
I mentioned to the plumber that our last hours had a Valiant and we'd had no problems with it. He said he really rates the Logic boilers. I figured he'd want to put something trouble free in as he won't want it breaking in 6 months and me phoning up moaning.
Vailant/Worcester Bosch seemed to be the go to options when I asked.
Check to see if you qualify for the boiler scrappage scheme