Thanks for the reply.

I've not checked the relay for fuses but it's a sealed little unit. I'll have it out and make sure I've not missed anything (obvious) tomorrow. I can't see how any connections may have come loose and everything looks good, bolts tight etc. There is nothing happening off the ignition, not even side lights when turned to park. I've got hold of a multimeter today so will see how the new battery reacts to load, other than that I intend taking every connection apart and sanding it down to shiny metal before putting it back together again. Don't know what else to do. Electrics are not exactly my strong suit so it looks like I'm in for a learning curve.