Scoot,
Thanks. To answer your questions:
1. My car is a v late 230; the flasher relay is the aluminium can under the dash. I know that coz I've looked and listened to it operating, but I did read about a later version (I have a feeling you posted on that thread) where Alfred and others discussed later types. My car blinks too slowly for it to pass the MOT Test (annual test for vehicles in the UK).
2. To be honest, the flasher blinks improperly most of the time with or without the engine running (the idle issue related to my old battery; I have just put in a brand new MB battery). When the blinker works incorrectly, it's slow, or the light just stays on. Sometimes it works properly, though.
3. Read up on bulbs, also, but a good prompt by you. I'm pretty content that the bulbs are correct. I will check the rears, but given the hassle of getting the front headlights in not so long ago, I'd rather replace the flasher in the first instance than try to take that lot apart (I know that sounds daft; you had to be there...). I rebuilt the headlights a few years ago and hope I would have had the good sense to use the right bulbs.
I have done a limited search on the Bosch PN, which is printed on the can (and is in the wiki), but I am limited by the sites I can see at work. I'll do a more thorough search at home, but I suspect that - as the wiki states - it may well be NLA given that it will have been superseded by a more efficient design. The current MB PN is also in the Wiki and comes up as the black plastic box. SLS also confirm that PN, although they’re out of stock.
I suspect that I may be in the business of rewiring the plug to allow me to fit the later type of relay, which is the black plastic one shown in the Wiki. If I can figure out how to open the alu can without destroying it, I may have a go at retrofitting the gubbins, but I suspect that the risk of breaking things may mean that I accept having to use the plastic box type.
Best,
James