Great news! It appears that Melissa is going to be released on DVD this year at Play.com. I asked Channel 4 last year and was told none was planned, so am writing for confirmation. If true, this must be the result of viewer demand, which is fantastic. Power to the people.
There isn't much info on the site but it says it's a 2 disk set for Region 2. The release date is said to be June 12th. I'd take it with a grain of salt, since the date for The River King was originally reported as October 2005 by Play.com, and it still hasn't come out yet in the UK.