I posted this in technical at the bottom of my thread, but I thought I'd make it's own thread as I thought it would be of interest here.
I wanted to convert my Mk1 from a Hydraulic brake light switch to an Electric brake light switch, as per the post 1976 cars. After finding out none of the parts are currently available to mount an electric brake light switch in car that never had one originally, my Dad kindly offered to make me a bracket. He thought rather than copy the original, which we only had one photo of, he decided to make something that would clamp on and be held by three 5mm grub screws. We used some scrap aluminium (hence the machined lines), which we bent to suit. Then tapped the 1/2" 20UNF thread for the switch and also tapped the threads for the grub screws and after some fiddling it all works as it should. We could of taken a bit more of the aluminium away and made it smaller, but it's not on show, so not an issue.
Using the grub screws obviously meant we didn't have to drill a new hole in an awkward position in the pedal box, or remove it. I used a genuine Lucas switch and the correct nut, both from eBay. For the wiring I used some 2 core cable for 12V, that already had a thin black PVC sleeve and ran the cable from the engine bay into the cabin.
Overall I'm very happy, as well has never having to worry about the old Hydraulic switch failing, the brake lights are much brighter. It's a win win as they say.