it can be ready in one day...it depends how many layers he appliesplastidip is quite cheap anyway,anyone can do it, even on their driveway ,have a look at some of the youtube clips
not to sure about drive way in windy wales to be honest! haha! but I have done a lot of youtube viewing and most say you need to clean the car thoroughly and leave to dry over night for best results, so a 20mile drive in the morning and then they start at 9am to be driving again at 8pm home I think it may not be the best thing but I am by no means a pro at this at all...