Back on topic, the RH lamp has been flickering more and more often, so given that I can't find the 2nd original bulb (I have already put the first back in the LH side as part of the fault diagnosis) so I went to the local motor factors this morning to get a new one - €149

, but following shocked expression I was offered it for €130. Have to wait and see if it cures the problem.
If it does, I'm thinking that the "genuine" bulbs I bought might have been counterfeit, hence only lasting 6 months against the 8 years of the originals. I did notice that the metal base, which is in two crimped parts, is loose on one of them. We'll wait and see.