If it's just clicking or you get nothing when you go to start, the usual culprit is the contacts in the solenoid.
A very straightforward job to do (remove starter motor) & a fraction of the cost of a new one.
An example here:
https://www.ebay.co.uk/itm/ROVER-75-...8AAOSwwbdWO6zG
The above is like I said just an example (automatic).