Make sure the red ignition light comes on OK
I had exactly the same problem and it was down to the wire that comes from the altenator to the dash, the alternater needs this wire to be OK before it will charge the battery. Sounds crazy I know, but a smart arse mate of mine saved me a load of aggro after I had swapped engine looms on a 24 valve conversion. It refused to charge the battery or illuminate the ignition light, ran a new wire from the alternator to the dash and it works fine

Mark

EDIT!

Beaten to it!