What a beautiful restoration. As a 10 year old I travelled in a relative's TD21 convertible with the same colour scheme as this one. Great memories. I thought they were designed by Graber of Switzerland? Thanks for the memory!
Alvis used the separate chassis principle till the end, so their cars could be sent to whatever coachbuilder you wanted. This one is by Park Ward in London. Alvis were popular in Switzerland in the 1930's - and became so once more in the 1950's, leading customers to use a local coachbuilder for the chassis that Alvis delivered. This was most often Carosserie Graber, who for many produced the best-looking Alvises. I think that the final Alvises (the TF21) were all Graber, but I might be wrong there.
Does have a lot in common with the Farinas, from the thumbnail I was 50:50 Alvis/VP Princess 4 litre R - IMO the Alvis with its smoother, more flowing lines has the edge from a stylistic perspective.