Frioch, heather ale to a pictish recipe - I had some of that last week -- lovely. I like the phrase on the label: "Brewed in Scotland for 2000 years".
I agree about Harveys. Ringwood brewery is also very good (last night I could smell the malt on the wind). And I've only just this moment realised that "New Forester" is one of their brews, so now I know where I got the moniker.
You could also brew your own -- it's not too hard to make a good traditional ale from kits or proper ingredients, and you'll know where it's come from.
Generally, the smaller the brewery the better.
Some pubs nowadays have their own microbreweries, and also some microbreweries let you make your own batch with their kit.