A land agent working in the area you want to move to will be able to help......
Down in Angus, Perthshire, Fife, southern Aberdeenshire 90% of farm sales are done through land agents with the likes of Galbraiths (as tattyMacintosh said), Bidwells, Retties, DM Hall, Bell Ingrams, Savills, Strutt & Parker to list but a few.
As well as selling entire farms, they will also sell land parcels but they may be able to shed light on any tenancy opportunities as many of them deal with large estates etc.
There is a lot of places on the market at the moment - some good farms and also a couple of very large estates being broken up too.