Cheers. Just doing something different for a day off....Been looking at a run to Bruges and back. Seems to work okay - And still time for a beer or two before the last one back to St Panc
If you're looking to have a ride on a Belgian "domestic" train, you might be better just going as far as Ghent, which is almost as attractive but less touristy than Bruges/Brugge. It's got a tram system to ride on too.
Or you could go north to Antwerp (another tram system), and admire the fantastic Victorian trainshed, with modern through platforms underneath.
You can get a Eurostar ticket to any Belgian station for not much more than the Brussels price.
But whatever yo do, try the beer; some of the best beer cafes have 100+ beers and require a "beer menu" to show them all. Each sort of beer comes in its own distinctive glass. Some are very strong, so although you'll be drinking less than a pint with each one, be aware that it could well be stronger than a pint in terms of alcohol. Look out for Trappist beers (brewed by monks) if you can. Lots of places sell bottles & glasses to take home with you, but if you're planning to do that and enjoy a couple on the way back on Eurostar, make sure you take a bottle opener with you; Eurostar do not have one on board (not when I've been in need of one anyway).