In the interest of shared knowledge –
I had a call from Gurit the makers of SP epoxy system. The answer they assure me is WATER. In it’s uncured form epoxy resin and hardener are water soluble. Wash it off with warm water (soap could be added but you then need to make sure that is cleaned off). After all that you could then use acetone if you want…
Given I have painted this on to bare wood there will be a degree of re-prep but small price to make sure job done properly. So tomorrow I shall break through the ice and get the old scrubbing brush out and go on attack. Second thoughts I shall employ small children to do this bit. Isn’t that what they are for?
They also gave me another tip: if you have lots to do have a few separates pots with the right mix in, do not stir and cover with clingfilm. When you need the next pot simply uncover stir and go. No reaction will take place until stirred thoroughly, even at the interface between resin and hardener as one simply floats on the other. Useful bloke.