Wise words on checking the details but the thrust of this debate (as appreciated by the civilian masses who do not understand our unfathomable ToS) is that you can be made compulsory redundant (non-volunteer) and be called-up at a time and place of HM's choosing. I'm sitting amongst a bunch of civilian friends this morning and they all consider this to be most unfair.
JTO,
Why do you consider that unfair? I don't see this as being for the situation where they've made a mistake and suddenly need more people in a certain branch. Rather, I imagine they'll set the required manning and then have it upset by WWIII, whereupon they need you back because you've still got the requisite skills.
Seems alright to me; I wouldn't expect to get called back for "we're a bit short, can you come back for a few years?" but I'd be happy to do my bit in the even of another GW1/Falklands etc.