Is It My Starter Motor or Battery That's Broken ?

the car was running fine i had parked it for around 10 mins. i went to start it but forgot i left it in gear
then it would not start at all. just made a click sound when i turn the key
it bump starts no problem in 2nd gear down a hill but it wont start from jump leads.
the cars a 97 1.4 corsa any help would be appreciated as i cant afford to take it to a garage

Suggestion:

Vauxhalls do this when they have a flat battery… I've had a few and never had a starter motor go, but a few flat batteries!
Mind, you say it won't start from jump leads, are the leads up to the job (Big fat heavy copper wires at least 10mm2) and is the donor battery up to it? Modern cars have small starter motors that require Shed loads of current to turn, and if the battery doesn't have the crank capacity left, then it is a no go.
Even though I have nailed my colours to the mast, a starter motor for a corsa is an easy and comparatively cheap find at a scrap yard and will cost less than a new battery, so what you waiting for?