Also, I know nothing about the state of interconnects between France and the Netherlands. HVDC under the quite narrow English channel might well be the most efficient route.
I also specifically remember 9 years ago during my aforementioned undergraduate report obtaining spreadsheets from the UK National Grid with time segments containing the direction and amount of power transferring via each interconnect (you're going to have to take my word for it... my copy of that data is long gone). These also showed exactly what I described, power being imported and exported simultaneously.
I expect there is a reason for this, perhaps arbitrage but maybe more likely some minimum power has to flow to keep connected sensors/relays/whatever from misbehaving, or some other engineering reason.
It's a bit like food where our wheat crop is down 40% this year but we aren't expecting riots because the rest of the world is up.
Countries with higher voltage distribution systems (there are a few 1 megavolt in China for example) have less losses, but you still don't want to be moving much power across entire continents.