Don't stress! The problems at Calais haven't been affecting Eurostar, just the vehicle shuttles, and there are other ways to get to LHR (albeit not as cheap).
When you check in with BA at BRU they'll give you your boarding passes for the VS flight and check your bags through. I've done exactly the same - all I'd say is it's worth stopping by the VS transfer desk in T3 flight connections or the concierge desk in the Clubhouse just to confirm you've arrived and check your bags are in the system ok. But all should be fine.
You should be fine short checking bags on the way back. There've only been a couple of reports of agents refusing - neither at MIA - and the worst case scenario is they'll demand a fee for doing it but the ex-EU savings mean you'll still easily come out on top.
When you check in with BA at BRU they'll give you your boarding passes for the VS flight and check your bags through. I've done exactly the same - all I'd say is it's worth stopping by the VS transfer desk in T3 flight connections or the concierge desk in the Clubhouse just to confirm you've arrived and check your bags are in the system ok. But all should be fine.
You should be fine short checking bags on the way back. There've only been a couple of reports of agents refusing - neither at MIA - and the worst case scenario is they'll demand a fee for doing it but the ex-EU savings mean you'll still easily come out on top.