You've got to get tyres as well. Always cheaper to pay the difference for the upgrade than to buy a fresh set and sell your own set. About £200-250 of that £965 will be in the tyres - 19" tyres will probably be £50 a piece nore than the 18"ers.
They sell the Austins for 1689 euros too, so 780 euro difference (£678+ £200 tyre money and you're not far off your £965)