(1) Differences training, signed off by a microlight instructor in your logbook. Expect this to take 1-2 hours, you can do it in your own aeroplane.
(2) Join the LAA and/or BMAA (the MW6T is looked after by the LAA so you will need full membership or they won't renew your permit).
(3) Personally I think that whilst certainly safe, the 6T has poor handling, mediocre ergonomics and crap performance. At least look to buying an MW6S which only has crap performance, or the MW5 (single seater) which is a much nicer handling aeroplane than either. If no particular thing about MWs, then right at the cheap end of the market the Thruster TST, Rans S4/5, X'Air 582, AX3, AX2000, Minimax are all much nicer aeroplanes with probably better spares availability as well (the 6T you'll be making your own in most cases!).
G