One of THE best looking kit cars ever made IMHO, but based on entirely the wrong base-car, sadly.
They are a minor cult among people that like this sort of a thing, but for £12K it would need to be a) amazingly well built and preserved, and b) have a very, very important history.
Quote from an owner selling one:
What’s it like to drive…
Terrifying, truly terrifying, but the previous owner owned her for 16 years and often commuted in her! Imagine being an astronaut in a makeshift space-craft, that roof electronically closes in on you in your tiny cockpit. You’re trapped. You’re sat back at an angle, basically on the floor and as you blip that peddle the exhausts growl, you fill the entire lane, as you set off you honestly don’t know if this journey might be your last. You need to be insane to enjoy it, you need to be mental, I’m just warning you. Amazing fun.
The moldy seats speak volumes…
googling trident led me to this 
Huge amounts of cobwebs and an 850cc Reliant motor.
Glad to see that there’s a roll bar on it
Most-used part of the car I should imagine.
You should buy it and fit a V12, there’s loads of room 
Bang on!
PS WTF are you doing up before lunchtime?
Shit the bed.
Furry muff 
Bastard love child of a 2CV, blimp era Micra and “does my bum look big in this?” Megane! 
You’re forgetting the Invacar in its lineage
A mate of my dad’s had one, he couldn’t lift his left leg into the car unaided so when he left the pub he always asked me to give him a hand, 9 times out of 10 he’d pissed down his leg
