I don't know why anyone would think Belgian made - I don't see any Belgian markings on the gun (and also not on the one in the linked thread). Neither the perron mark nor the usual elg or the typical star-over letter Belgian inspector mark. Unless it's a complete fake, including faked Birmingham marks, I wouldn't doubt the British origin.
I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.