Thanks BEANZY
Ive Connected the downstairs old existing house sockets (MCB)to the RCD side of the board. It has been working ok for last hour.
Normally the RCD trips within 5 to 10 mins when i had new ring connected.(downstairs sockets new side).
Just connected new side also to see if it trips. Ive now got both rings for downstairs sockets on RCD. will post results later, maybe this will help.