Good thing about Belgium is it’s only 1/2 hour out of the train tunnel.
there is a canal in adinkerke (sp) where most of the brits go on a booze/Fag cruise.
I have a friend who is from Belgium but he has been on the missing list for 6 months or so.
I could ask him for a few ideas but he’s not an angler so could be hit or miss
this could be a good starting point
https://www.angloinfo.com/how-to/belgium/lifestyle/sports-leisure/fishing