I have also tried this, with rather pleasing results, so I'd heartily recommend the experimentation to fellow posters. So sincere thanks to those contributing to the thread which gave me the idea
I had around 20cl left from a 'cheap and cheerful' Signatory Vintage Islay Cask Strength (5yo, 58.4%) that I was struggling to finish - I found it very young, feinty and pretty harsh (yet I liked the Ardbeg Very Young
So... to 20cl Sig Vintage Islay (5yo Caol Ila) I added around 10cl of Laphroaig QC and 5cl of Ardbeg Uigeadail and let it marry in a 35cl/half bottle for a week or so and voila.......... very nice and a huge improvement. It has picked up the smooth, sweet peat and wood influence of the QC and a hint of the deep sherried smokiness of the Oogy. A much more palateable and pleasant dram but still a fairly heavy peat-hit and less mono-dimensional.
To take this concept further I may even just keep topping this 35cl bottle up with CS Islay and similar and as such have a living islay vatting.
Home-vatting experimentation gets the