TS on the forum, found another source quoting JJ as being attached to Telstar, in The Ticket.

"Con O'Neill, who played Meek in the stage version, reprises the role in the film, which features JJ Field as Heinz Burt, Meek's peroxide protege who played guitar with The Tornados before going solo, and Pam Ferris as Meek's landlady Violet Shenton, whom he murdered before killing himself in 1967. Kevin Spacey is also in the cast, along with Ralf Little, James Corden and Sid Mitchell."

IMDb has also updated the cast list further to include JJ's name.