Ford Fiesta 1.1 1995 Starting Problem

My Ford Fiesta Mistral 1.1 1995 will not start.
When the ignition is turned, the ignition lights come on as per usual, but as the key is turned to start, it just clunks once then will not turn over again.
Recently tightened the fan belt and replaced the battery to alternator wires, as the battery hadn't been charging while driving.
Since then (for the past 2 months) its been fine.
I hadn't left lights/radio on overnight, But today it wouldn't turn over.

I have just forked out for a replacement clutch, so am hoping its something easy.

Any ideas what it may be? Alternator? Battery Charging? Ignition Switch?

there should be an earth cable from the battery to the gearbox just above the starter motor have they replaced that?your charging system needs checking and your battery needs checking it could really do to go to a garage to have these checked ask friends neighbours for a local garage that they recommend