Not to mention relying on fans to fill in major plot holes - why did Maneet turn mole?
It may well be that there is a specific plot point around this which needs to be held back till the next series. In the meantime it's sufficient to work out that she was almost certainly either threatened or blackmailed into it.
How was JamieNotJames recruited?
Why does it matter? It wouldn't particularly add anything. If they have to give a massive back story as to how every baddy gets involved, it would become very tedious.
Why didn't Ros go to the doctors with her rotting arm?
Well, she did eventually. She presumably didn't for some time because (a) she though it would heal up on its own and (b) she didn't want awkward questions about how she did it.
How did ArnottNotArnold recover from a fractured skull, broken pelvis, broken ribs, broken arm and manage to do so well in a wheelchair but be unable to wash up?
Partly because, as pointed out, his sink isn't at wheelchair height. And probably also because he's in constant pain and exhausted, and just can't be arsed after a day pretending that he can cope just fine.