@templar2k5...£15 a metre what a liberty.Try some local vinyl fitting companies.I would not use the Hammerite on the car but your call...
No you don't need to primer the car,only where there is repairs or bare metal.Wet flat the panels with soapy water & fine wet and dry.The green underneath will be a good base & save you paint.
Get a little compressor from somewhere,have a practice.You'll save a lot of money & get a better job!!