Central Locking - expensive or not

Hello,

Been to look at my Landy today and its mint however is has a few security issues.

1st one is no central locking or fob locking? I have 2 keys and a fob. Fob does nothing keys open one door at a time. Is this going to be an expensive fix? Im handy with tools and have a fellow landy owning autospark at work so could between us we get it sorted?

Also the rear boot lid does lock - is this normall ?

For me it was just the passenger door working and no central locking I got a £25 central locking kit that was on ebay with two fobs and it works a treat. It doesn't set the alarm but all the doors lock as they should, just plugs straight it according to the garage...

Been playing today and been through the RAVE manual AND the ETM to try and work it out but keep drawing blanks on which unit to diagnose lol.

So the car is a (lovely) 1995 RRC Vogue. The alarm appears to work and goes off if i lock the door then reach through the open window and unlock it, the roof lights light as I open each door but the central locking doesnt do anything on any door. Not even trying to use the Keyfob yet. If i lock the drivers door i can see the O/S indicator flash BUT the passenger door doesnt do anything

Is there anything i can try or can anyone shed some light on where to start with a voltmeter ? looking at the ETM, I cant find a suitable plug to test. Ive got 2 boxes that the ETC points to behind the glove box, i pull the plugs to test and the plug config doesnt match the piccie - any one any ideas?