If the engine isn’t turning over, start with the starter relay under the bonnet, switch it with the fan relay which sits alongside it. It won’t be the main relay-which sits next to the fuel pump relay as this powers the ECU and controls the fuel pump to start/stop.
If the relay is ok, jump the Starter Solenoid to prove the starter motor, if it is ok.
Check the fuse , if the fuse is ok
Check the earths, if the connectivity is ok.
Check out the Spider immobiliser control unit behind the dash at the far right - a black box about 2” square. They are notorious for dry soldered joints.
If the Spider Unit proves ok- you can buy a link out block on eBay for about a tenner.
Check out the 10AS immobiliser .
