96 Galaxy GLX
2.0 Petrol

I got in my car the other day and drove as normal to the Tesco nearby.
The car stated first time as usual, never having a problem
Coming out of Tesco and starting the car up .... but not turning. Dead.
battery was eliminated as it was replaced just 3 weeks before
Turn the ignition and 'click'. Nothing. Lights on the dash as normal. Just no turn over.
I had to bump the car offf to get her going
Did some Googling and pretty much the answer was Relay #30
I got a new replacement relay, inserted it and guess what? Nothing.
Starter Motor? Started to rock the car as you normally do. Nothing

Got a Haynes manual and the theory goes along the lines of:
'Turn the key with your lights on, if the lights dim as your turn the ignition, then voltage is getting to your Starter Motor. Therefore the problem is the starter motor'
My lights did drop when I turned the ignition

Starter Motor? Ignition? Any other ideas?
Best place to get a Starter Motor?

Thanks in advance