They don't.

I was on a BT-operated flight to ZRH past week, in J, nothing "special". I suppose the usual procedure: if you are in Y, seat blocking works or doesn't + everything on the ground is as always (your space in the MUC lounge, pre-boarding...). On board, if you need a pillow or blanket or whatever, just ask (if they refuse, then you can ask them "even for ULTI customers?" - and they usually will comply, at least that was my experience when BT crew refused things on LX flights and I looked puzzled "even for HONs?"). If you miss your pastic cup of Champagne as extra courtesy, well, those are the vagaries of air travel these days...

The seats on the BT A220 are slightly less comfy than the AF ones though, and no internet on board. But that's the same thing for everyone, not just ULTI.