Simply not closing a plan won't result in S&R in the UK.
Hmmmpppff. What then is the !@#$%^&^&*** reason for filing a flight plan? Suppose I actually DO go missing, how will "the powers that be" realise?
On a recent flight through Germany, that went awry due to low cloud, I was much reassured by the FIS inquiring whether I was still on the frequency! I'm not sure she would have done that if I were not an a flight plan. It is nice to know one is being looked after.