Hi, what can you tell me about living costs, i.e. accommodation and food, for an officer in the Royal Artillery?

Hello,

Costs for accommodation and food are the same across the Army. They change from year to year though.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/820973/SFA-SLA-Accommodation-Charges.pdf
If you scroll to the last page you can see charges for SLA (Single living accommodation), how much you pay depends on what grade your room is (ie how nice it is).

Food in most messes is now pay as you dine, meals have a set price if you choose from the core menu, but sometimes the mess will have a bar menu which is more expensive.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/854802/CRL_Published_Rates__1_Jan_-_31_Mar_20_.pdf
The green table at the top has the cost for each meal.

Your accommodation is taken directly out of your pay, your food and drinks are added to your mess bill which most people arrange to pay monthly via direct debit.