Shed made the point much better than myself. The SE are "spoilt" for choice with cross channel access. The only Loco flight to Ostend was indeed by RYR from Stansted.
I did the flight from MAN to Ostend in a Laker 1-11 in 45 minutes back in 1975.
I've been through Charleroi & I'd rather connect to Belgium /Europe via Ostend.
It's a rotation that could be squeezed into a schedule & probably relatively cheaply too.