Yes, RHIP slipped at the same rate that I advanced civilian grades and the contentiously named EMR.
Not only First Class rail, but service vehicles and drivers. At JHQ I occupied a Gp Capt post and started with a nice car and a service driver, soon changed to grumpy German driver, soon changed to drive yourself, soon changed to drive your own battered little Ford or Opel.
This was of course in parallel with down and down and down grading for quarters. Back in 1961 at RAF Nicosia just about everything was provided on scale. By the time I did my last march-out JHQ 1996 there was not a lot on the inventory to check.
Still the most important RHIP aspect was the salary and the pension, after all is said and done.