[papajam]

Thanks for the responses and because of them, I found out the following;

1. Series 1 Euro 1750 GTVs have dual filament bulbs in the large outer headlights that are known as 'Bilux' bulbs, not H4s as I had mistakenly called them. The Bilux bulbs (predecessor to the H4?)have a different globe shape than the H4s and I think the bases are slightly different too. The small, inner lights have H1s.

2. The Series 2 1750s and Euro 2l Bertone GTVs have H1 single filament bulbs in all 4 headlights (as confirmed by wolf).

So the 105.21/22 diagram is now complete and will be posted in the electrical diagrams of this BB shortly.

The bulb on the left is a Bilux; the right is an H4.