Sam Riley, who has won raves for his leading role in Control, has joined the cast, along with previously announced Ryan Phillippe and Eva Green. The cast also includes Bernard Hill, Susannah York and Art Malik.
The film is about four lost souls whose worlds collide in the parallel worlds of contemporary London and the future metropolis of Meanwhile City.
Jeremy Thomas is producing with co-producers Alexandra Stone and Nick O'Hagan. RPC's Peter Watson is serving as executive producer.
Writer/director McMorrow previously won the TCM Classic Shorts Film Competition with Thespian X.
Jeremy Thomas said: 'We've had wonderful experiences working with first-time directors such as Jonathan Glazer and David Mackenzie to bring their talent to audiences around the world and we are very optimistic about Gerald's ability to make a powerful and attractive film.
The crew includes DoP Ben Davis and production designer Laurence Dorman.
Franklyn has financing from the UK Film Council's Premiere Fund (which chipped in $2m), Film4 and Aramid, with international sales being handled by RPC sister company HanWay Films.
RPC's slate also includes new projects from Bernardo Bertolucci, David Cronenberg, Whit Stillman, Phillip Noyce, Vincenzo Natali and David Mackenzie.