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Well got the bit this morning, but it isn't overly clear how it's fitted. No instructions (and the bag was open). Have come away from the workplace, half expecting to have to return it. Sat here, I think I may have figured it out.
The olive must have to go onto the chromed "blank" end, rather than on a copper pipe as one would normally expect, and then connect directly to the thermostatic valve. That then leaves the end with an external screw thread to fit to a copper pipe. It'd only be fittable directly to the radiator if the full extension of 60mm was required since the sliding tube part unthreaded end appears to need to pass through the threaded end and then be swallowed inside the pipe. That's just weird and uninstictive. What odds that it'll be ok ?
I may try it later this week. Trouble is after trying, it won't be returnable any more.