You will prob still go under RFA 96, even if you asked to go yourself. Not that employment protection means alot. Depends on your employer. Have you asked if they will appeal. If they say yes they will appeal, then hedge your bets accordingly.
There is possibly an unresolved issue here - if a reservist volunteers for compulsory mobilisation then is it really compulsory ? It is possible (although I've no idea how probable) that an employer might interpret volunteering as leaving. The resulting unemployment tribunal would be interesting.
So if I was you I'd tell work they're dragging you off kicking and screaming and make damn sure your unit say the same.
The two times I have mobilised I have "VOLUNTEERED" and have been 'COMPULSORY MOBILISED' both times. I think its to encourage people to volunteer knowing that they will be afforded the same protection as their mate who did not go voluntary. Then again I may be talking complete bollocks.
"I would like to be mobilised." is a statement, not a request.
"Please mobilise me." is a request that could lead your employer to argue the toss about re-instating you once you get back. (Though only if your employer either doesn't like you or prefers to keep the "stand-in" that he employed while you were away).