Thank you for your reply. Unfortunately I still couldn't get the base panel off, and looking under a better light there was no screw in the long recessed tube. I again tried a little gentle leverage both at the front and rear, but still to no avail. So I forgot the base and sought entry via a different route.
HERE IS THE SUCCESSFUL WAY TO THE SUPPLY CORD CLAMP:
1) Ensure the unit is unplugged from the mains and place the iron somewhere safe, off the base unit.
2) Remove the three silicone buffers from the iron stand and the three screws now revealed. Lift off the iron stand and set aside.
3) Remove the two further screws you now have access to, and carefully remove the rear cover. This gives you access to the mains cable clamp.
Reassemle in reverse order.
Simples! - once you know how.
With best will in the world, I cannot rate the info you've given as worth £27, as basically I landed up cracking it myself. But as someone who used to be on 'weekend-call-out-standby' I appreciate the fact that you were there.
All best wishes for 2015