I bought my online couple of years ago from arnold Clark. They had send me few videos and I think you have at least 1 year warranty. It was serviced by them as well for few years . When I went for service here the mechanic told me that the car is in a great shape with lots new parts and a very good buy.
It was a very strange experience as it was brought from Scotland and it was click and collect type of purchase. Never had I thought I would be buying a second hand car like that. You pay small holding fee I think I paid something like 50-100£ for transport to London and you have few locations to choose from.