Sorry for the late arrival, I'm a newbie here but I’ve been cold smoking salmon for a while so i thought I'd add my thoughts on the Video..
Ref the Market: As has been said here, absolutely take cash, and also a large cool box, a dripping salmon does nothing for a car’s interior. (Same goes for Smithfield, but remember you have to be out of London by 7:00am to avoid the congestion charge and if you do go to Smithfield be prepared to buy in bulk for the big savings, a wheeled cool box or a wheeled travel bag and some bubble wrap for insulation is recommended. ( Cow, Pigs and Sheep are heavy!) )
Curing salt: I now always use Kosher salt, it has no Iodine and I swear tastes better. I buy it in 25KG sacks so it’s pretty good value. I also always dry cure, Salt,& Sugar mix. Plus a bit of Dill and White pepper directly on the fish. I cure skin side down and cover the entire fish in the mix, less at the tail and the head, then leave between 12h and 24h. You can prod it and feel when it’s done, in Steak terms it goes from “Blue” to a “Well done”. Next rinse gently under running water for at least 20mins. Unless I’ve caught the fish myself I don’t freeze beforehand.
Leave for a a day for the pellicle to form then I’ll smoke, usually with Alder dust, but I’ll always smoke the fish flat, I just think it’s safer. What I’m trying to avoid at all stages it to tear the flesh. On the video you can see where this has happened in a couple of places. I use a large Prow for the smoker and I usually refill it once. Different woods burn at different speeds so the time will vary.
Then I tend to leave it for a another day in the fridge then cut the side in half, vacuum pack and freeze.
I’ve rambled on long enough!
cheers