Thanks for all your replies.

Do the boots have to be replaced in pairs? For me its the one side only thats "about to split".

The story now is BMW refuses to repair it because it is only "about to split", so my question is when it does, then what? - the service adviser said, then we'll consider whether its a wear and tear item. No straight answer if you ask me. A quick call to a local garage and I'm told its a 2hr job for an inner boot change which would cost less than £150.

Sure sounds like they wanted me to change the boot and fork out the ridiculous £800, then when they were told (and so subsequently checked) that I had warranty, changed it "don't think its a covered part" and then, when I pulled out the warranty booklet to "wear and tear", then "its not actually split yet so no warranty" and now to "its alright, dun worry". I'll do without the aggravation and not buy the extended warranty for next year.