During the summer life jackets, life raft and PLB. During the winter exposure suits as well. I generally always cross in the airways and for the UK to Europe crossing this actually always leaves me in glide distance. For the UK to the CI which I do weekly my out of glide distance is around 10 mins. Regardless I take appropriate equipment for sea survival. As an offshore boat skipper I attend a sea survival course every year which includes deployment and getting into a life raft.
Crossing the Channel in the UK with an EPIRB leaves me no more than 30 minutes according to the coast guard from a helicopter.
I also carry flares and water dye marker. In addition to my McMurdo Fast find GPS PLB my aircrew life jacket also has a 121.5 locator built into it. The ditch bag carries a mobile phone in an aqua-pac, an aviation Icom in an aqua-pac and an Icom marine radio in an aqua-pac.
I won't fly over 'hostile' territory single engine. By hostile I mean something like the Canadian 'outback' where it is difficult to locate a downed aircraft and the emergency response is minimal.
I will fly over European mountains at airways heights as the exposure time again is limited and surprisingly there are a very healthy number of glide clear options. I would not want to cross some of the big US ranges single engine.
The problem with you North Americans is you apply North American geography to our terrain which is pussy cat stuff to what you have. We have little in the way of things that stick up to run into. Our ground is generally flat and open and we are minutes away from rescue over 98% of our terrain.
Even crossing the med which is warm water the longest crossings to anywhere are the Islands and they are around 120nm around 50mins in my aircraft and at airways heights around half that time is away from glide clear.
I am happy with the risk mitigation that I take . It is not perfect but then nothing in aviation is. Of course I would prefer taking a twin but at our operating costs a 2 week holiday touring around Europe would settle the 3rd world debt, reduce the places that I can visit etc.