Maybe I'm missing the point here, but could you not bring the car back to the UK for six months and leave it with your family?
You'd know it was safe with them and someone could take it for a run every now and again for you.
My son is also going to Afghanistan in September, and I imagine his car will be left with either me, his dad or his girlfriend.
Mind you............... he doesn't own a Cupra (unfortunately!)
This would be the most obvious and easiest option...
Unfortunately (well fortunately) I bought my cupra tax fee because im posted over seas which means for the 1st year i shouldnt have it in uk for periods as long as 6months... Something to do with the fact ive de registered it with dvla and registered it as being a british forces germany owned car.... Pain in the arse