Thank you for the replies. By "light switch module" I mean the headlight switch to the right-hand side of the driver. namely this:
Would that need a t4? It's the immediate and obvious source of a drain as it is constantly illuminated.
The car doesn't have the high-line sat-nav installation.
The replacement battery is a Yuasa Silver HSB096 80Ah/760amps.
Yes you will need a LSM matched to your mileage, I had the err on the dash caused by the previous owner swapping the LSM. I managed to get one matched from the 75and zt forum on a recon exchange basis.
I believe the LSM holds data including mileage and the vin number for the car, if the data doesn't match it shows the err on the trip mileage on the dash.