Hi Dave...
When flying VFR outside the US or an area covered by FSS and you climb above the transition altitude ATC gives you the instruction to request IFR (at the transition altitude), however without FSS there is no way (I don't think) that you can request a switch from VFR to IFR. So you just plod along for several hundred miles with ATC reminding you every few minutes to request IFR. In fact I was on final for landing at LSGG, received tower clearance to land and then he told me to request IFR as I was nearing the blacktop. Not the end of the world, but annoying. I know, I could start out IFR, but in 1958 most of the flights were VFR.