World of Whisky (sub brand of the big duty free stores) have a lot of open bottles, if you start gentle enquires about some of the pricier stuff they soon start pouring ..... both the bit on the right and left as you walk towards the south lounge complex.

At the moment I would recommend Balvenie tun 1401 Batch 7 for traditionalists, (duty free only) and Bowmore springtide (again DF only) for Islay-philes.

Not many bargains to be had these days, and some rip-offs too

Sometimes there is a set-up with promotion of a specific brand, recently this had been JW (shudder), in the past fiddy or big mac