If you have the correct paint code from the VIN plate, your local paint shop will match the colour. The only issue comes when you are matching old panels with paint to new paint/panels. As you are doing the whole are i think you will be good.
Don't bother with halfords though, even your local motor factors will do paint cheaper if you are looking at the rattle can route.
The issue is the preporation and how/where you are spraying the car.
As Mr Haynes says "bodywork is relative to the time and effort applied"
Good look, keep us posted.