londonbound86, you had permission to stay in the UK for six months, you stayed for four. Entirely legal, and you shouldn't have anything to worry about. There is nothing wrong with staying longer than originally intended - I'm sure you're not the only UK visitor whose plans changed while in the country.

And stut, I don't think you are right about airlines having to scan passports for Immigration. Airlines have to check passengers' identities and ensure that they have valid documents for the place they are travelling to, but that's all. I certainly didn't have my passport scanned by anyone last time I left the country - checked in online, went straight through to the departure lounge at NWI, had someone glance at my passport at the gate - that was all.

Also, no records are kept of people who leave the country on private flights - the only time passenger lists have to be submitted for private flights is when the destination is in the Common Travel Area (Channel Islands, Isle of Man, Ireland), and those records go to Special Branch (=police) only, not to Immigration. (All a hangover from the IRA days)

To get back to the original point - londonbound86, you have nothing to worry about as you did not overstay.