Been looking for a reasonable run that doesn't take up much or any holiday, and found this:

https://www.google.com/flights?hl=en...22*2.GBP.62722

This should be showing a fare of £628 for 360 TP - arranged so it's basically one evening B2B to/from Jersey on the Thursday which I can do easily after work, then the latest flight to LUX on Friday (so take the afternoon off), and then open jaws back to LHR over the weekend via LUX.

Better still, the equivalent fare prices up at travelup for £600, so there should be around £60 price promise cash back. My claim is just in, if you want to wait and see (or just book the OTA fare and save £30)

I've just booked it between 5th and 8th of Dec, it seems to run from early November until at least the close of the year, you can find it by looking for LUX->OTP at around £440 over a weekend, then construct the other legs around that. Probably also works from other start points, INV for example. You can do this with a return to MAN wrapped round the LUX bits rather than JER for about £700 but it needs more holiday because of the way the timings work out. Similarly you can replace OTP with KEF and probably some other 80TP destinations. Adding a return to Jersey on my dates didn't make any sense, the fare shot up by quite a lot.

Book using the BA multicity tool (to get the price promise, it must be on BA.com), and book legs for JER->LGW; LHR->LUX, LUX->OTP, OTP->LUX, LUX->LHR