So the tyres have been on for a day now and I'm so happy with them
I went for 235/70 R16s which aren't much bigger than the old ones but having new grip they seem to fill the wheel arches better.
Even better they appear to have stopped the 60-70mps wheel wobble I used to experience, though thats probably down to balancing rather than anything else. Also a lot quieter and I did a skid test on the sma estretch of road, before and after and its as huge difference, soooo much better grip.