Hi Andy,
The brake switch is available on ebay from time to tine. They were fitted to all Land Rovers Series One (and many more British cars from the 50's) and the Lucas part number is LU31281B.
The boots are available from BODA. (still I believe).
I can take a photo of the stering column mount as I only recently removed the dashboard on my Arnolt Coupe. The fixing is rather crude and easy to replicate.
My mail is
kenneth.andren@gmail.com
Kenneth Andrén
404X 3086
404X 3137C