HOST NOT FOUND ON MASTER SERVER it reads when I try to set up a host or go to the self same host I've had for over a year. Even before the X patch came in without problems.
All it offers are XF GTI and XR GT cars - all the remainder are greyed out.
I have S2 and full access via Single player and even on the multiplayer at the public tracks but NOT via the self-made host just for head to head racing with a friend.
What can I do please? I have a BT Voyager external modem.

Maybe this helps?

A dedicated host or ingame host?

If it's an ingame host, check if there isn't accidently 'S1 Mode' set in the menu