Hi, good have you on the forum, welcome alongThis weekend I went to see a prospective Approved Used 19 plate cavansite blue MP, thanks to all the info on here I checked the roof. As you may have guessed it was littered with blisters, the MB dealership was blissfully unaware of the fault. I've not committed to buying the vehicle until I get a guarantee that the roof will be replaced.
I have no doubt that you will be supported by MB in this concern, but you could try ringing MBUK customer services for confirmation.
(I expect the dealer and MB will say that they would need to inspect the roof prior to making a commitment but so far I don't think anyone with a roof issue within the warranty period has been rejected a repair)
Good luck and happy camping!!