Thanks Matt - Unfortunately the Lucas 594 are too big.
These come in Clear, Amber and Red and the lens is 50mm dia. I might see if they are 'E' marked. Can they be plastic and 'E' marked?
Front Marker Side Lights 5Watt OR Reversing Lights 12volt Durite Clear Round | eBay
Geoff - Land Rover 'Defender' are 73mm
Why do projects get bogged down with trivial stuff like this? Arrrr...