What alexbrett said. I would say add £3k to the first annual after your purchase (ballpark figure).
Are you going to be the sole user? If yes, and if it goes on G- reg, the 50h check has to be done after 6 months even if 50 hours not flown.
My personal advice would be to buy an Archer, not a Warrior. True 4-seater, handles roughly in the same way (just slow it down in a busy circuit, you don't have to with a Warrior), goes 10-15kts faster and all that for a similar price both in terms of initial purchase and maintenance. Oh, do I recall correctly that the Warrior's engine has a hollow crankshaft whereas the Archer's one is solid? One more or less place for corrosion I am told - no experience as I fly a Dakota with variable pitch prop so that has to have hollow crankshaft.
Welcome to the minefield
/h88