This sounds great if I'm reading it right. I left just over 3 years ago and my last 2 tours were about 18 months each. In the first case I travelled 32 miles each way daily and on the last tour 40 miles each way daily. The difference between my HDT and the HMRC rates of 45p / mile (first 10,000 miles) and 25p / mile (thereafter) will be quite substantial so the tax rebate could be sizeable. I have payslips here, but no assignment orders here at home. Perhaps a chat with my nearest friendly PSF?
Any more details would be much appreciated.