Not British, but trained in English law. Seminal case in Anglia TV v Reed [1971] 3 ALL ER 690, CA. If you repudiate a contract for the production of a show which Appellant Reed ( of Brady Bunch fame) did, you are liable for wasted costs, but not usually for losses of profit as that cannot be properly quantified, the show might have been unsuccessful.
It’s just low budget tv drama that goes from season to season - no long contracts, no one wants them. What’s different about the US market is that any tv hit is a cash cow, and it’s milked until it dies. Not the case in the UK - Misfits was popular enough (for Channel 4) but no big deal, certainly didn’t have the budget to prevent cast moving on to better paid work if offers came in.
One British show that has suffered from this writing model is Downton Abbey. Lord Fellowes came up with one series worth of posh soap opera when he was given the opportunity. It became a huge success, but he hadn’t heard of the American concepts of “showrunner” or multi-season character or plot arcs. Many of us think the writing for Series 2 suffered; initial reports indicate Series 3 is somewhat better. But only somewhat. Reports on the Christmas show will be available soon…
In a recent *Vanity Fair *article, it was said that Fellowes had never had a co-writer; his wife is his “editor.” Diligent fans found co-writer names attached to two series 1 episodes–but none since then. Might better writing have helped convince certain cast members to stay?
Moffat, et al., have more of a clue about running shows. But Doctor Who is a special case; it is expected that the cast–even the leading man–will change…