Should be £25 a day subsistence - though that will cover breakfast and lunch as well if you're not accessing service catering. You might also want to check that CILOR isn't being provided instead if it's a week long exercise in an area without service catering.
Minor correction. The £25 is Day Subs (assuming in UK) for Lunch and Dinner. Breakfast is part of Night Subs. Your hotel should have been booked through Defence Hotel Reservation Service and B+B included.