Its okay, not a 'gotcha'. If it was all combined and tax free, then I wouldn't commute.
I've found a large .pdf called 'AFPS - Invaliding' and on a Med Discharge, the Veterans Agency do all the assessment, then this all goes the the Pensions people at Glasgow.
For 20% +, it looks like your earned pension is now enhanced and called a Service Attributable Pension (SAP) or Service Invaliding Pension (SIP)
Gonna have to write a letter to Glasgow...
But I'm a bit anxious that I don't get to plan my finances until after I leave!