Please can any one tell the best reasonably price suspension struts for both ends of a locost built to the Haynes build a sports car manual.

Protech are recommended by a lot of people

http://www.procomp.co.uk/shockdyno.html

Valving is to their own specification and units are balanced in pairs.

You need a damper made to the correct length for droop.
You need a damper made with correct valving for a light car.
You need a damper made with thinner oil for fast rebound.
Don't forget to fit correct bump stops or you'll lose your sump ..