JSP754 (Tri-Service Regulations for Pay and Charges) Ch.9
Temporary Assignments
09.0108.For Service personnel serving on temporary assignment accommodation charges will be raised as follows:
a. When public accommodation is used at the temporary assignment unit:(1) Service personnel who occupy SLA at the place of temporary assignment will, unless otherwise exempt under the terms of these regulations, pay the charge appropriate to the SLA occupied. If they retain the SLA at their permanent unit/station these charges will cease from the date the SLA at the temporary unit/station is occupied and restart once it is vacated.(2) Service single personnel who have been authorised to live out at their permanent assignment station will not pay accommodation charges when they attend a course or an assignment of 12 months or less, provided they have a continuing commitment to pay a mortgage/rent and their property has not been sub-let.
b. When public accommodation is not used at the temporary assignment unit, Service personnel will continue to pay for any retained accommodation at the permanent station.
c. When Service personnel serving in the permanent garrison in Northern Ireland are absent from the Province on a temporary assignment they become liable to pay accommodation charges under normal rules.
Personnel on Temporary Assignments
09.1009. Personnel Paying Food Charges on a Continuous Basis. Personnel who are paying food charges on a continuous basis at their normal/permanent duty station/parent unit who proceed on a temporary/ detached assignment will continue to pay the relevant food charge, if applicable, at the temporary/detached assignment. This includes those temporarily assigned to a PAYD unit, where they will be eligible to receive the Core Meal.
Sorry to be the bearer of bad news, but basically it's in the regulations, and has been for a while now, so you're going to have to pay.