Thanks all for the suggestions and info
I have cleaned the slide up and find the screws are standard 2ba cup point grub screws about 10mm long. There are no ball bearings or plugs and the ends have not been rounded. 2 of the screws were missing which helps to explain the sloppyness.
I intend to retain the 5 existing grub screws and replace the missing 2 with cap screws which I am now awaiting, I may have to run a die down these to make the threaded part long enough to reach the gib strip.
Its worth mentioning that the gib strip is located axially with a small pin 1.5mm dia driven through from the outside of the slide engaging with a slot in the outer face of the gib.