Thanks Shrew, You are right, just wanted to take the easy route if someone could help identify the right bit. Now done it the hard way:
Length is 70cm when open, weight is 5Kg to lift, so 50N with 10mm ball socket.
I got one from a specialist store; they seem to be a lot cheaper in the UK £26.99
delivered in the UK. This is an adjustable pressure one so I can set it as needed.
https://www.strutsdepot.com/product/...ce-gas-struts/