With a transfer of terminals, 35 minutes is definitely pushing it to the limits. Asuming an on-time arrival at the gate there are various scenarios at BRU. The worse case is that you can be unlucky enough to park at Terminal A (Schengen) even though you're arriving from the UK - in which case you will be bussed to Terminal B (non-Schengen) to clear immigration. You then have to make the long trek on foot back to Terminal A, with possible delay at security. What is particularly annoying is that you get dropped off by the bus somewhere half way along the rather long pier on Terminal B. A similar scenario can happen on the return when your Schengen flight will park at the non-Schengen terminal. There's no way of knowing in advance as it all depends on that particular aircraft's planned rotations that day. As mentioned above, be sure to advise the CC of your approved but tight connection.