Really good work - people who have never done a full custom may not appreciate the challenge. You have met that challenge. I agree with misterNML: all that paint design would hide the pure lines and beauty of your work.
This one has been a lot of work! The headlight lamps in the Revell Ferrari California kit look a lot like your Triumph front turn signals, just a little larger. These kits can be found for not many $, and styrene might be easier to work. The 3d pieces might look better with a small coating of something like MicroMark CR300 resin or DecoArt triple thick glaze to give a smooth finish.
Good Work! I've been thinking about a similar model and have collected some relevant photos. I could not find any record of a four-seat T26 fastback. Except for this recent barn find designed by Pierre Saoutchik. It was done on the longer Record chassis and the other fastbacks were apparently done on the shorter GS chassis.
Fantastic! You're making it look too easy - this is really challenging work. It's starting to have a bit of a Prowler vibe. To make it more practical, you could use a perimeter frame, drop the seats as much as possible, and bump out the firewall for leg room (see a Jag XKE).
If you want to strengthen a join, apply a fat line of regular superglue along the inner side of the join, then cover with baking soda. Only do this where you won't want to remove any, as it sets up almost like stone. I do this quite a bit, since I only build customs myself.