wpms has been replaced by afip in 2012 which is the same rate as pip etc, it depends on when you served as to which you qualify for and as bigdave says invariabley it is a pain to get. it took 3 years and appeals and the intervention of the rbl to sort mine out.
that said i am currently waiting for assessment of an additional injury and have been waiting for an appointment for a year. as i discovered when my back blew up that my award doesnt include my ptsd or my back.
the whole thing is complicated and affects all sorts, there are now 3 i think different pension schemes for the forces as well so working out what you qualify for can be fun. i was royal army pay corps for most of my service so dealt with some of it as part of my job, but it even confuses me.