Rocket Wash, I have had a similar issue with a new hand wash company near me, had my car washed there and on arriving home noticed paint had been lifted off at some stone chip points. Result is a £400 paint repair. Never happened on any car before or any other wash sites. Having a metallic paint finish not so easy to do simple touch ups to any stone chips. solution probably invest in my own pressure washer and / or hand wash myself.

What may have happened if your previous car washing firms used a jet wash is that doing so started the process off and the latest one just got rid of the last vestiges of the clear coat (or lacquer on alloy wheels).

The other thing that may have caused this is use of more corrosive cleaning chemicals which more esaily get rid of dirt, but especially sap, bird droppings and tar, but if its not removed within a short time (as alloy wheel cleaners state - normally 30-60 seconds contact time) and/or used as a general cleaner for the rest of the car, then you're asking for trouble.

Additionally, we're always told to gently hose the car down with cold water first to loosen any dirt, which reduced the need for stronger cleaners, and, more importantly it hopefully washes off larger dirt and grit particles that could, if you clean it with a sponge, use the jet wash on full power or use an auto wash facility without a pre-wash (hose down), the larger and sharper particles will just scratch the paintwork, wheels and windows.

Many 'cheapo' cash wash facilities (you know, those 'pop up' ones) may well not bother to read the label when buying/using their cleaning agents or don't pay attention to good practice. By the time you notice the problems, you're back at home and there's almost certainly no redress available, especially if the car wash owner (and his mates there) get annoyed at your assertions of mistreatment of your car.

If you want it done properly, either do it yourself or use a professional cleaning firm with a reputation and a business address, not just some blokes in a retail park car park or a beat up old garage that popped up with a hand-written sign last week advertising £10 car washes.