On 29th January South Western Vehicle Auctions will be selling a '29 M type described as recently fully restored to a high standard ( so it's not mine ! ) It is apparently known to the Register (910) and has been in the same family for 50 years . There are lots of photos in their on-line catalogue for the high standard of the restoration to be visually checked.
The boot lid follows a dead straight line as opposed to the subtle curve of an original which is all too frequently overlooked. It can be corrected, I believe.