I would say a fair bit over £10k, nearer £15k, I have a full set of Palitoy 20 Backs, all graded to 85, I recently re-valued them due to their rarity, you just don't seem to see many at all nowadays, I had my graded Power Droid (AFA 85), valued at £3000 but after speaking to a good friend of mine said it would command at least £5000 as he doesn't know of any other Power Droid graded to that level.
If you add on to that a Death Star Droid, which you hardly ever see, say £3000, that puts it up to £8k for two, throw in an AFA 85 Greedo and you are well over £10k!!!
I personally think that the Palitoy 20 back run is becoming increasingly hard to complete, even the so called 'easier' ones, R5-D4, Snaggletooth and Luke X-wing are demanding high prices, nowadays a great complete run to have!!!