So my preference is generally for an islay or island whisky that's rich and complex and unusual.
In a Speyside or highland, I often like the rich, sherried malts that are like cake in a glass -- glenfarclas 105 was great. In a lighter, fruitier dram, I'd look for complexity and don't much like malts that are too linear and 'boring'.

Would anyone care to recommend me a good highland/Speyside whisky, irrespective of price? I'm trying to look out for something new but don't know what to go for.

I've had my eye on a glenlivet 18 year old but I hear that it's not really worth its £50 price tag...?