Dude you need to chill!!!
The £520 on your person would have me wondering! Anything over £1000 and no real excuse and it can be seized. Personally I wouldnt carry that amount with me.
As for the stop, not sure of the location but I stop MINI's all day every day as they are being stolen at the moment and you never know.
Also, leaving at 90, not really the best idea was it!!!