Why don't you transfer the NCD to the MG and start the Fiat 500 off as the newly insured car. When I first bought mine I registered it in the wife's name, I pay £323 with Aviva. I changed from an Admiral Multicar policy last year when they hiked up all their prices, remember loyalty counts for nothing these days with Insurance Companies.
Road Tax on my 04 reg is £260 (may have gone up to £270 now).
Nich.
PS.... Forget the trees, they are overrated.