Complex sentence: The TMi flat was no longer the key feature of the programme and production had moved from the studio facilities in Leicester Square, London to studio 9 at BBC Television Centre (previously home to CBBC, 1997 to 2006) which has remained since.
Split into simpler sentences: The TMi flat was no longer featured because TMi had moved out from the studio in Leicester Square, London. Now the programme is broadcast from studio TC9 at BBC Television Centre (CBBC's old studio from 1997 to 2006) which has remained since.