Hi,

Regarding your driving licence, don't bother getting an international one, I did, and it was a waste. I converted my UK one to Qatari one as soon as I got my RP.
NO test necessary, only an eye test.
Not sure about the other bits you are asking about, but I'm sure someone else will advise you.
I claimed my tax back when I left though... Definitly do that if you're staying out of the UK for some time...

Good Luck