If it is the switch contact that has failed, not a wire lead to/from the switch that has broken, etc.,
it is just possible the contact has only gone too high resistance to carry the current for the bulbs direct. In which case, it just might drive a relay that could then drive the bulbs indirectly.
It may not be much of a chance it will drive a relay, but if it does, it saves replacing the main/dip/flash/indicator switch, which ain't that cheap [
https://www.ebay.co.uk/itm/232450675596 ... SwOPhgHRKF] and is a bit of a pain to swap.
Even if you do have to replace the switch, it's still worth considering adding relays to drive the mains and dips, as it takes a lot of load off switch contacts, and isn't that hard to do (don't mention Scotch Locks as an option for splicing the relays in, it upsets Steve).
Graham
That wasn't a diagnose but recognizing someting what I have seen 100 times before.
All Dolomites, Stags, 2500's have the same switch and 4 main beams and all these have the same trouble of melting the plastic around the contact that has the blue wire on. The blue white contact is the moving part and moving the stalk the other way it connects to the purple wire contact and then the lights flash.
This problem was already around when Dolomites were new I believe and that's why a lot have relay's fitted on the mains. Good switches are rare and I regularly get the question to sell LHD type switches to fit on RHD cars to have the standard layout but I do not sell as a few off all I have are decent and most are already melted or not working at all. The RHD versions obviously the same. So when you have or find a decent switch, save it with some relays because good original ones are rare.
Jeroen