I have done some flights now in, out and then back into CAS. Handovers seem to go fine.
Thus my solution to the pop-up IFR quandary is to fly IFR, but remain OCAS and not bother anyone.
That's what most people do, and this is why few would bother to do an IR if they didn't want to fly outside the UK.
But, in the southern UK especially, flying OCAS usually means flying low, which exposes one to uncomfortable or hazardous weather e.g. cumulus layers in the summer or icing conditions in the winter.
