Hi Llewellyn,
Keith at Eurovettes has just provided me with a complete kit including instructions for my '92. The amber light lenses on mine are the square-ish ones rather than the round ones like on yours but he might be a good place to start. I haven't fitted it yet - I'm prioritising the '72 build at the moment - but hope to get round to it soon.
Just watched your video on the clean of your C4 - you must be really pleased with how it has come up, both outside and in. Looks terrific.