The best deal will be on 15" alloys with 195/45R15 tyres. Make sure you get the 45 pofile tyres or they'll catch on your car.
Most of the deals new start at around £299 for 4 from either Motorworld (Me) Or the Dreaded Big H
You'll need that tyre size, and the wheels need at Offset (ET) of around 38 and a bolt pattern (PCD or pitch circle diameter) of 4 X 108