The controversey on these tends to revolve around early season fishing (mainly in Shetland) and the question of whether at this time of year the fish are kelts. You will need a Salmon rod licence, even if fishing in the sea for migratory fish. I think I remember John Bailey writing about catching Sea Trout in Norfolk creeks using stickback livebaits. I would try Rob's advice and also give the fly a go.
Jon, u let my secret out!! I use the fly these days. A sandeel imitation fished on a neutral density line. I fish the coast up here in Aberdeen, but I constantly have to look over my shoulder. I never keep the fish, but I could get done for poaching.