It's at 8pm on Channel 4.
Hope Tamarmole is getting some royalties tho seem to remember the answer was no... :(
As with all of these things you get a one off payment (if you are lucky - its amazing how many people want you to do this sort of thing for free). You also have to sign a release form which means that they can do whatever they like with the footage they have shot. If I was on a royalty for the Edwardian Farm and the Wartime Farm I would be a rich man given how often they churn the repeats out.
On the bright side the production company had a very nice copy of the Devon Great Consols plan printed which they kindly gave me at the end of filming. (We filmed a sequence up at DGC which wasn't used).