I myself, don't notice anything around me, except that we have more people coming from Brussels doing their shopping in Waterloo and combine it with a visit to the Lion. As Brussels is still in lockdown, they come here it's only 15 km and we have the same stores.
As an anti-terror police operation was underway in Brussels to search for Paris attackers, police asked residents to not share details of the operations on social media on Sunday evening. So instead, Belgians shared a lot of cat photos.Have a look here
This is typical Belgian humor! Nevertheless, we all don't understand nothing anymore ! On one side terrorist alert remains for this week on level 4 which is the maximum and therefore the lockdown should be valid for everybody but no, the schools are open and the metro is running. From people living in Waterloo and working in Brussels, lockdown or not the majority went to work.
The tourists take pictures of soldiers and policemen and tanks with the beautiful background of a historical building ! Very special as souvenir.
The Brussels' population is fed up with these exaggerated long lasting security measurements and therefore a list is published in newspapers where you can read what is open or not !

I had no time yet to go to Brussels and check myself, but I looked at the Webcam of the Grand'Place yesterday morning and it looks rather normal to me !
As the weather was and is so bad during the lockdown, people would have stayed home anyway!
The terrorists are certainly rubbing their hands and are happy with the result caused by their Paris attack ! (except maybe they didn't appreciate the cats !)

according to the UK Newspaper "Independent"