Just spotted bubbles of rust on my front wing wheel arch and checked with a bodywork specialist today who said this is a problem with BMW,s. Quite surprised to see this on a 6 year old car and there was nothing there 8 months ago when I bought it. I also wash it regularly. Specialist says whole wing will need to be done and section of arch repaired before spraying cost about £200. My last car was an Audi which had a 10 year guarantee on paintwork but I dont think BMW has this.