Incidental Expenses
Can't you still claim your £5ish a day ie if you are away for over 24 hours (even if staying at Mil Accom)? If so, does this cover your food & accom charges? It's been while so I'm not too sure.
You may wish to post the question on e-goat under the Shiney's area, where I'm sure there will be someone who can give you the gen you need.