Well - ordering a Seal Mate certainly did the trick.
half an hour after I order one and one of the tubular scraper type ones I thought 'I'll have one last go' and used a smaller plastic drink bottle.
After some more faffing and gentle persuasion I finally gained entry and tidied up both fork seals! The secret - for me anyway - was having a curved section of plastic and keeping it tight to the tube and edging it round and gently , but forcefully, with the edge of my thumb nail on edge of 'scraper'.
So, I now have two seal tools, as yet untried, but the homemade one finally did it after many attempts

There are plenty of pics and vids out there, but here the bottle I used and the tool I made.
For me it was the twist and edge of thumbnail that convinced it to work.
Hope that helps anyone similarly frustrated.