The screw that actually fits to the machine, I believe is a t27 screw. Do you know what size is it as I don't need a whole kit yet just the screw. Also is it a self tapper or machine screw?

If it's the lighter coloured screw this is a Pan head self-tapping screw IS-D4x15 - https://www.lsengineers.co.uk/catalog/product/view/id/9276. If it's the darker silver screw this is Spur gear/chain adjusting screw kit - https://www.lsengineers.co.uk/catalog/product/view/id/10475. The sizes are not listed.