[cheshired5]

Thank you for your kind words and I'm glad you find them useful.

Some further testing for you.....

If you have a multimeter, definitely follow the starter testing video but in addition, get a voltage reading by probing the small spade connector on the starter solenoid.
It should be zero when not attempting a start then battery voltage with the ignition key in the starting position.
No voltage at the spade during a starting attempt is an issue with the starter relay or spade wiring.

If there's voltage at the spade but no click from the starter solenoid, tap the solenoid with a piece of wood or heavy plastic during an attempted start.

Additionally clamp the red multimeter lead (set to DC Volts) to the starter body where it meets the engine and the black lead to the earth lead bolt on the chassis side during cranking.
Anything above 0.2 Volts DC suggests a knackered earth cable.

Better still, if you have a jump lead, connect it to the starter body at the engine and to the chassis.
This bypasses the main earth lead.
If the starter then turns, the earth lead is definitely toast.