The local Co-op filling station is selling car washes at half price at the moment, so a wash polish and dry is £3 to £5, others are charging £3 to £6 without a dry.
I usually run mine through a soft brush wash only every month for £3 ish, and every 4-6 months I take it to some Croatian guys who give it a real good hand wash and hand dry it, vacuum all of the inside, and shine the dash , doors etc – ‘ in and out’ for £13, but that’s for a SUV , other vehicles cost less, from £8 for the same service?
When the cars are new, I use the brushless car wash at Magor services on the M4 just over the Prince of Wales ( Severn) Bridge, for about £9-10, not cheap, but no marks on the new paintwork either.