I usually just give them the PPs and make sure they know that it is british pounds and not USD. They've always just applied it as a credit, not an adjustment, without any prompting needed. I would imagine they post it the same as they post BBs, so i guess it depends on if the hotel posts those properly too.

Fremont Marriott gives $164 flat..same as last year even though the pound has come up quite a bit. But its better than nothing.

Stays always post and I always pay the balance after PP using a Marriott gift card (recently been purchasing them from marriottgiftcardoffer.com - 10% off)