It seems to be exclusive to Sainsbury's but they are selling 70cl of it for £9.99, States 1/2 price. Also jim Beam 70cl for £13.
This seems to be a review although the bottle says 12yo golden rum cask
Glenmorangie 12 yo Golden Rum finish (40%, OB) Colour: straw. Nose: very clean, fresh and lively, on fresh butter and flower nectar. Tons of fresh apple(golden delicious) and a little oak. I must admit I dont really get the rum, but maybe thats good news. Its simple, not complex at all, but very clean and full of youth. I like it! Some apple skin develops after a few minutes. Mouth: very nice and clean attack, on apple juice, vanilla and oak. A little bourbonny. Again, not too complex, but nicely balanced. Some caramel and some milk chocolate do emerge after a moment The finish isnt too long but nicely balanced, getting quite malty. Again, its very nice whisky. Much nicer than all wine finishes from Glenmorangies core range, thats for sure.