I had that on the passenger side. I replaced all pectron relays in the SCU, you can access the SCU behind the center console, under the radio.
I found a youtube where it shows how to do it.
You really need good soldering tools to do this without damaging the SCU, otherwise I would take the SCU to a specialist. (google is my friend : https://www.technozen-electronics.co.uk/mg-rover-pektron-scu-repairs-parts/)
With new relays the door issue was solved, and also interval on the windscreen wiper was working again.
So probably no need to take the door apart.