You will need to board your floor first otherwise any imperfections will show through as the vinyl will mould itself to the floor.
it is a labour intensive job - fitters will expect around £10 per sq metre to do this for you.
If you DIY remember use ring shank nails (38mm) and nail every 15cm - 20cm in all directions. 4mm ply is approx the same price as hardboard and gives a better finish...



