No worries, Kieran.
I just realised that, as it's a Mk.1, my advice about the anti-beartrap was useless - as the anti-beartrap wasn't fitted until the Mk.2!
I know Alan mentioned this already, but there is a large, metal piston weight in front of the spring on the standard set up. These can get jammed inside the piston and take some persuasion to remove. Did yours definitely come out when you removed the original spring?
M.A.D. FOR IT!