When I got my phase 1 Mi16 it had been standing for a long time. Boot lock didn't work, it shut but didn't lock on either the remote or key. It turned out to be the lock motor, but I was lucky, mine was stuck open, another 405 at the breakers yard was jammed shut and there is no access, hence it was at the breakers.

If yours starts playing up, change it. Inside the lock there is the motor that can burn out, but also a worm drive that pushes the connector rod in and out. On mine this had seized, no idea how this happened. (working ones pull and push in and out). It's fiddly enough getting the thing in and out with the boot open, impossible to reach even with the back seat out so be warned.

The boot lock, petrol flap and rear doors all have the same type of motor and at a breakers the boot and petrol flap are the most accessible. There is a metal rod on the petrol flap that just pops off (spring washer fixing) so you can use it on the boot. If you cut off the wires (one blue, one yellow) about 10cm from the plug it makes life easy testing against a battery to make sure the electrics work. Plug will only fit one way. Phase 1 & phase 2 are the same, the wiring numbers change.

Part number is A90493, made by Rockwell