There's a charter operator that has a BN Islander (16 seats) who can fly to LM from the impressively London Ashford Airport (Lydd) but I suspect that this won't come cheap.
It may be possible to avoid paying positioning charges (Flying the plane back between trips) if the plane has no other bookings, but Le Mans airport doesn't have fire cover tor a BA 146, and a 737 might not quite have enough runway to be comfortable.
If I'm coming next year, it'll have to be a Fri PM / Sat AM - out, SUN PM back jobby.........