Past posts and username suggest the OP is Jersey based which for UK destinations offers them some alternatives to BA (not LHR however):
Blue Islands
Loganair
EasyJet
Eastern Airways
For beyond UK destinations I'm not sure there's going to be a wealth of options (at least on thru tickets) for them to choose from without having to split/nest tickets and all the fun that entails if plans change.
Virgin might codeshare with someone via MAN perhaps. There'll also be seasonal opportunities with Lufthansa Group via MUC.
Other than that I suspect the OP will find themselves back on BA sooner than they'd perhaps like.