As mentioned before, a one-off use of fairy liquid is unlikely to cause irrepairable damage. Using it every weekend on the other hand is completely different.
As for petrol, if I had unexpectedly run out of gas and Morrison's was the closest, I'd head there and put enough petrol in to reach Shell!
Plus I used APC all over the car yesterday at 1:4 dilution! Here's the end result:
Clicky