The question is pretty tenuous at best - there are very few bikes you would take from the UK to Europe without lights that you'd want to be riding any distance on the road anyway...

Unless you are talking about a vintage bike, or [and I'm presuming] an MX bike you've registered for road use, pretty much every motorcycle has a head and tail light fitted anyway, so you'd be covered as far a daylight-running-light requirement is concerned... and even non [street] homologated Enduro and Trails bikes come with a simple head and tail light fitted these days - quite possibly for just this reason (ie. road use between trail/trial sections, since their effectiveness is pretty poor at night).

I'm sure if the bike was clearly designed and/or of an age not to have lights fitted (rather than you've simply taken them off) then you'd be able to explain that to any police officer who stopped you and queried you - but as Backofbeyond suggests, is that something you really want to deal with in the first place?

Like a lot of these 'issues' - their relevance is very much down to context... if you want to trailer an MX or stripped down Trials bike to France and ride a few green lanes during daylight hours, I'm sure in practice you'd be fine... riding your MX bike through the centre of a busy city at rush hour is another matter entirely.

Personally I'm not sure why you'd not want some sort of lights on your bike anyway? - not least as it gives you the option to ride for longer - particularly if you do get caught out towards the end of the day - and you can fit a very compact LED head a tail light (with a DC reg/regulator) to pretty much any 'off-road' bike these days.

Jx