Seems like a nice care but I'm not sure I would spend £7k at a service and then sell it for £15k soon after. Surely better selling for £8-£10k without the work. More chance at selling a slightly worse one at that money than as best as it can be for £15k. It is like buying a house that needs a bit of work to add value. There is no room to do that here at £15k but there would be at £8-£10k.
Are these representing the best value at £15k? I know mine was a fair bit more but it will always be worth that much more than something like this example, should look after me just as well if not better and will be much easier to sell. It is the less desired early model/revision so would expect this to be more like £12-£13k tops. I guess when they get older it starts to really vary and the gaps on values get much wider.
All my opinion of course! I'm still learning