Hmm it does seem like the B8s are the common link in the rears feeling a bit waywardMichelin Pilot Sport 4 on the M for me every time. Tried a few different ones over the years but these have been the best for me. Interesting what @swamper says about the pressures, I too find the rears dont grip/ride so well at the correct pressures so run them a bit lower and makes all the difference, maybe its the B8s that cause it?
Funnily enough last night I was looking at my usual tyre website Camskill, used them for years. Unfortunately they don’t do the Falken 510 tyres I wanted in the sizes I require.Tyreleader.co.uk has excellent selection and can send avon tyres to your local garage to be fitted. Prices and selection are best I've seen also.