It's a Plancraft Stingray:
Boat History http://www.plancraft.co.uk/boat_history.htm#Stingray.
Thank you very much for posting the brochure!!!
I am sure it is a Shakespeare Starfire although I have never seen or heard about an outboard version:...
I think it is a Sunliner Marine Sunsport (5,4mx2,1m, approx. 450Kg, up to 200hp) from the middle/late 70s.
Try to get more information on your...
I think the boat is a Seaswift, built by Seaswift Products Ltd.
Have you asked Klas yet? He runs the website you took the brochure pic off. That would be my first idea. You could also ask...
Perhaps this picture helps to estimate some of the dimensions: