The MCC is a box ticking exercice, nothing more... I did it on the cheap, in a fixed based FNPTII. Worked fine, save myself some money (the instructor was able to renew my IR on it so that was a double whammy)) and ended up flying Medium and Heavy jets.
It really doesn't matter what you do it on and certainly in the UK, you can't fail it because it is not a test.
Now unless you have an interview/sim ride coming shortly after your MCC, I would say the benefit of practising in a full motion sim beforehand is probably limited. It is not to say that once you have an a sim ride coming, you shouldn't try to book yourself a sim session somewhere.
The first time I did on a 125. Worked fine.
The second time I bought FS (the latest whatever it is) and it worked fine too (as it was basic scanning the "needles" an expensive sim wouldn't have made the slightest difference).
I think guys that the situation you are in requires you to keep your IR running, your medical up to date and some hours coming in your logbook.
Depending on how long you will be in the job market for, this can be all very expensive so saving 500 pounds now, might come handy later.
I/R renewal 300 pounds perhaps. Medical 100 quids=> That 's you current for 12 months. Not bad when in the application form they ask. Are you current ? and you can tick the Yes box.
Sure the idea of handling a Tristar sounds appealing but you should concentrate on a getting a job first. Being out of currency renders your licence invalid, regarless of an MCC done on whatever.