Haunted Bookshop -- strong, lots of natural burley flavor, no casing.
Old Joe Krantz -- strong, similar to Haunted Bookshop, but a touch sweeter from the VAs.
Morley's Best -- top-notch burleys, similar to those in Haunted Bookshop, plus some good sweet VA and a portion of Latakia.
For a totally different style (milder, sweeter), I second the recommendations for Aged Burley Flake and Wessex Burley Slice.
Prince Albert is also pretty good, with a mild, nutty burley taste, but with a noticeably sweet casing.