Thanks for the comments - the brakes seem to be behaving themselves, but will keep an eye on that - had a thorough service recently and was given a clean bill of health! I suspect my tyres were duff as you suggest Rob - see comments about inflation below. My son replaced all the tyres in Scotland and has just driven back to London without any issues, although it poured with rain the whole journey so not likely to have been problems with overheating? We checked the tyre pressures on the three remaining original tyres before replacing them and they were all over inflated which suggests the others which failed (probably but obviously not conclusively!) were unlikely to have be under inflated. I have come to the conclusion that the tyres were duff and were fine for the short journeys we have done to date, but did not fancy a long journey! Also worth noting that the 140/70 R12 tyres that BJT recommend can be replaced with 155/70 R12's which are about 15mm wider and 21mm larger in diameter! There are many more tyres available in this size with more choice of load index etc. Now to get a new mud guard!