Thanks for the info. This seems to bare out what somebody has said in a Alphard Camper Facebook group. I may have to bite the bullet and replace all 4 tyres as they are all as imported, the rear ones were an advisory on the MOT.
Thanks for your advice Rojie. After a lot of Googling and looking at reviews I found 225/55/R17 101V Michelin Primacy 4 tyres at a good price online and so I've decided to change all 4.