Yeah without a doubt. Clark is awesome. Decent guy aswell, but TBH its only polishing a car, not exactly rocket science!
There is a bit of science behind it and they have LOADS of experience and tools at their finger tips. What would the average detailer do when they find out the Impreza they are detailing has weird paint and the polishes start sticking/bonding to the car. Takes quite a bit of confidence to take a rotary to a £30k car...and they do Ferrari's etc.
Polished bliss do pretty much 95-100% corrections which is amazing. Most people couldn't afford to pay someone to get that level of correction as the time involved is huge. In 3 days it took to detail my car with a local detailer we got my Clio to about 80-90% correction and that cost a lot. They are also based on the outskirts of Aberdeen, which has rakes of people with too much money and not enough time.
For most people a good valet is enough...maybe a bit of correction here or there/more thorough clean. Need to tailor the services you offer to the customers that are available. Not reason you can't make it work.
If it takes 2-3 hours to give a car a good clean you'd be wanting to charge in the region of £30-40 to cover costs and a decent wage. I'm not sure I'd want to spend that much money when I can achieve the same thing in an afternoon.
There is a guy who owns 3 jet wash machines in Aberdeen. They are always busy with people popping in £1 after £1. I've seen him empty them, I'm not sure how often he does it, but there was A LOT of coins. Most people will have seen the guys in big multi story car parks who wash cars for £5, not bad idea. We used to have a guy who came to ASDA with what was effectively a car sized paddling pool to catch the water. Think he ran the jet wash from his van. £5 for a quick blast and scrub. Do 4-5 cars an hour and it might be worth it.
Basically you might make a bit of money detailing...no doubt about that...but you might want to look into building a solid base for it to work on 'just' washing cars...but doing it well.
