Generally I take my car to Guildford (near where I work), as the lexus dealership is pretty slick and they have spent countless hours doing stuff that Southampton are (not to put too finer point on it) pretty bad at like taking pride in their workmanship etc. etc. (Did I mention that Southampton Lexus were responsible for half of the contents of my sump leaking onto my drive....). Actually I take all that back, the reception staff are excellent :)
Overall I take my car to Southampton because the cost of servicing is 30% cheaper than Guildford (anyone else notice this HUGE price variance?).
With 1 month to run on my warranty I'm tidying up the car so I'm probably pushing my luck anyway. If I don't trade it in, i'll hit Lexus Guildford for some wheels, they're great people. Shame they're so expensive!
Anyway, with 2 months to run on your warranty I'd say go for it! My wheels have a couple of light marks on them and they didn't care about that as its the finish thats the problem (I seem to remember seeing other posts from people that have succesfully had wheels replaced with dings on them).
I actually can't see how Lexus can legally charge you for warranty repairs post event if they decide that it isn't valid given they have your wheels and won't return them. I wonder if you have to sign anything.
I pushed Lexus Southampton and they did buckle, eventually after being a bit direct with the technical guy. You should win, but it seems like they are using this to put borderline cases, or maybe people at the end of warranty periods away.