Hi.
Can you please give more detail of EXACTLY what happens when you try to start it.
You will need to describe what happens when you turn the key such as: nothing, a slight click, a rapid clicking noise, the engine turning slowly etc
Then you need to say what happens to the lights as you turn the key. Do they: stay bright, dim as you turn the key, or not come on etc
These are just the starting pints, that we need
Out of interset, are you depressing the clutch fully as you turn the key (even in nuetral)? And, are any of the warning lights coming on once it runs?
Edited to add: Even thought this may not be directly battery related, have you checked that each of the cells in both batteries have the correct amount of distilled water in them so that they properly cover all of the plates inside.
Plus, have you made sure that the battery terminal connectors are still on tight, and covered in Vaseline or grease?