Hi Dave,
A couple of Belgian that I think are worth investigating, both are the equivalent of a CC or C&CC site in the UK:
Camping Blaarmeersen (Gent) - 4 star - probably the best camp site in Belgium, and has an on-site restaurant and shop (high season).
Camping Ypra (Kemmel) - 2 star - half way between Ieper (Ypres) and Armentieres - couldn't be any closer to what you want to do...
A note about the Belgian star rating - 2 star means C&CC or CC type facilities, pitches of around 80 or 100 sq metres. 4 star doesn't improve on the 2 star standard, except it has more things on site - like a cafe, or restaurant, or shop, or pool.
Both are in the ACSI guide - so you should be able to get a discount with an ACSI card...
And both are in the Vlaams (Dutch) speaking region of Belgium...
Camping Blaameersen is really convenient for visiting Gent and Brugge, but it's a motorway hop from Gent to Kortrijk and maybe too far for what you want to do...
Robert
On my commute home from Rotterdam, I'll often stay in a family run hotel near Brugge - and I love this part of Belgium. Nice people, good food, great beer.