Attempt 2:
As I guess everyone would expect, besides this forum I visited a large fish and marine aquarium supplier in Henlow (UK) at the weekend and had a very good chat with one of the chaps who builds, stocks and maintains their own display tanks. (and who incidentally sold us ours) Based on the various input from the forum and this supplier, I have listed below the actions we are taking and why:
1. The salinity seems to be the main immediate issue - we brought it down over the weekend by simply topping up with RO, today will see a 15% water change which will take us further along the path to gently getting the salinity back to normal.
2. Adjusting the water pumps seems to have helped with the surface scum, that along with an adjustment to the skimmer. The surface water and the water in general now look very clear.
3. The carbon filter has been in since day 1 (6 months or so), it gets changed today and every 6-8 weeks thereafter.
4. Clean up crew: have been advised to wait until the salinity is back in a normal region as the shock may kill any new snails we put in now.
OK - here's where it seems to be a bit controversial given some of the comments on the forum... Whilst at the aquarium centre in Henlow, the chap above who builds/maintains the tanks said the following about the anemone and lighting.
* The lighting we have in our little tank is (he says) entirely adiquate and in fact optimal for it's size, he said it was the same intensity lighting they used in all their DT's and showed us under the lids of the various display tanks that had an enviable array of coral, anemone and fish. (I note wontonflip's comments but the guy was actively dissuading me from buying the extra brighter lights and saying to stick with what I've got - IMHO he's either straight-up or a pretty rubbish salesman! :-))
* If the Anemone is in a weakened state - which I guess it is, moving it to a different tank with different parameters will almost certainly stress it even more, better he felt to leave it where it is, get the tank salinity and water quality back to normal and it will hopefully recover.
Obviously we are still very new to this, but the above seems a pragmatic first few steps based on what I've seen, but I'd welcome any more observations particularly if anyone feels we have missed the point somewhere!! (sorry for the !!'s seems like it's a bit of a secret language with you all :-))
Rgds - Tom - Head_stock