I would suggest ON-001 or ON-010 for late night operations.
You can operate from the public parking lot on both summits, and have a lot of space for even an 80m antenna.
(I don’t know if 40m will work for UK contacts, depends on the distance, and QRM is heavy in the evening)
The other two, I wouldn’t stay in darkness, they are rather deserted places.
As for accomodation, I cannot recommend much, I always travel with AirBnb, and have stayed in several good places (send a private mail for more info on that).
There are some hotels near both summits (001/010), but I have no info on those. Otherwise, Eupen is a nice town to stay, maybe someone else knows a good hotel there … G4OBK ?
Another tip : hotels just across the border, in Germany (places like Roetgen, Monschau, Simmerath), often offer rooms with half pension, for the same price you will pay in Belgium or Luxemburg, for just a room with breakfast.
A search on booking.com may find you a good deal.
But they won’t serve you food if you arrive after 10 p.m. of course … and it will be a detour on your intended route I guess.
Luc - ON7DQ