Well I finally sorted the problem of the lights. When I bought it, one of the outer headlights had got a stone chip. It was supposed to be replaced by the seller for the MOT but it wasn't. I bought a new light (I thought) and decided to swap them as the MOT is due again. It's all a bit of a faff as I keep the Strada in a lock-up a couple of miles away. Anyway, the new headlight was too big as it was 7 inches, and not the 6 inches (150mm) fitted to mine.
I tried to remove the glass on the old one to spray the reflector, but broke the glass.
Having searched everywhere I couldn't find a replacement.
There had to be way round this. There was! I bought a couple of inner headlights from what I believe to be a Jaguar, probably a 420G. These had mounting holes in about the right places, but they only had main (sealed) beams. The good news is that they were
5 3/4 inches which were used on many British cars in the sixties and seventies.
I then bought a pair of sealed beam conversion units for a Vauxhall Firenza. These accept H4 bulbs and have a pilot light. (I only chose these as they have flat glass rather than domed, but others would fit, like Ford Capri or P6 Rover)
I removed the adjusters and fitted the bowls with nuts and bolts as the bowls have their own adjusters. I did fit three nuts to each bolt to give me further adjustment if necessary.
The lights look right at home in the grille, and I now have a proper Strada headlight for sale.
If I need to change one of the headlights in the future I can get a pair of the conversions for around £30. That's around a third of the cost of one Carello unit, and the only ones of those I could find are left hand drive.
It took a couple of days to get the bowls fitted correctly, but is was definitely worth it.
I'll post a picture once I've put the grille back on the car.