Same as any other tour I've been on. One of my more memorable Mess Meetings was in a hollow in the sand a couple of minutes walk away from BHQ in the outer reaches of Kuwait. No mess....no pool table..no bar..no accom (less a roll mat at a wheel station).
You should pay reduced rates but you will pay subs for the period you are away for a Mess that you are a member of.
Unless you are infering that you have no access to a Mess and you are in the UK?
I am sure there is something in QRs that if there is no physical mess then no you don't pay a mess bill. That is what happens at our place. We currently don't have a mess and our financial balance from previous mess bills is in it's thousands. Hopefully when we eventually get one it will be gucci, either that or robots will be running the army.
Sergeants' Messes 5.747. Membership
a. Every warrant officer and staff or other sergeant is to be a member of the sergeants' mess of his unit, and a single member may be a dining member. Membership is optional for those holding the local rank of sergeant.