I just took another look at the transfer company I found via Google (I won't mention their name but search for < pension transfer uk canada > and its the first hit), they do make it sound feasible. You need to pay them £25 for the guide then 0.5% of the transferred amount.
As for NATS not letting you take the money out, I am only passing on what I was told when I enquired of the Pensions people in NATS.