I think life jackets will ,in the event of you becoming unconcscious ,float you on your back with your mouth out of the water. A PFD/bouyancy aid will simply keep you afloat, not neccesarily face up !!!
Didnt realise there were any laws insisting on anything been worn anywhere in Europe. Must be difficult to enforce. an impact vest,many harnesses and all wet suits offer some level of bouyancy.
Been a couple of times I wished I`d worn impact vest; two broken ribs could have been avoided !!!