Frog_ATC a couple of responses to your questions.
1 - A UK PPL is not allowed to fly VFR over the top (it is a restriction on his licence)
2 - When a UK pilot talks about 'Airways' they normally mean the UK airway system which is almost universally Class A (hence only available to full IR holders)
3 - Most of the volume of UK airspace is Class G, where as I would guess most of France is Class E. Within the UK there is no real facility to get an IFR clearance for Class G and any radar separation service needs to be negotiated with each radar unit (if available at all!).
4 - Interestingly a UK PPL (without IR or IMCr) is allowed to fly IFR in Class G (most of the airspace he would use) and is EVEN allowed to fly in some types of IMC. Specifically, does not need to observe the cloud separation minima of VFR.
The combination of all of these is a UK view that hitting someone else in the open FIR in IMC is a vanishingly small possibility. The US, where I learned, has a view you have a high possibility of Crashing and Burning if you are IMC not on an IFR flight plan (similar to the view you have expressed).
Interestingly, the British don't seem to have hit another plane in Class G in IMC since around WWII, yet have the same depressing regularity of aircraft hitting each other on fine VMC days.
Finally, this hazy combination of IFR/VFR rules (which in many cases have no material difference), licence privileges (which are not straight VFR only or VFR + IFR), and the rigid separation of Class A airways vs. the rest results in much more casual (confused) views like - 'I am VFR (i.e. not on an IFR flight plan) but IMC' a non sequitur but you can understand why the pilot says in (because a well planned Class G VFR flight in the UK is going to be equally valid as an IFR flight - with NO CHANGE AT ALL on the pilots part)