Battery replaced under warranty.
Everything looked good, started a couple of times, left it for a while, still started Ok.
Thought everything was hunky dory.
Went for a short drive (about 2 miles) let the car stand for an hour and back to square one, exactly the same issue (alarm, door locks all Ok, no dash lights, no ignition)
Called out the RAC thinking it must be the alternator not charging (and the 2 miles was enough to drain the battery just enough even though it's new it could have been sat on a shelf for a couple of months?)
The RAC guy listened and thought that what I was saying was a possibility so he put the battery booster on it, no change, he then spent another 15 minutes looking it over, figuring out where all the wires go and checking the fuses.
Finally he pointed to the 150A fuse in the fuse holder connected to the positive terminal and said he thought it was probably related to that, he tested it and all was good, but he noticed some corrosion, he wiggled the live lead.
Key in the ignition, dash lit up like a Christmas tree. :-)
so he stripped and cleaned all the contacts put it back together and now it seems Ok.
Apparently the lead feeds the fusebox under the bonnet, so no power on that lead means no power to any of the power hungry bits of the car, the other bits are fed through the fusebox next to the steering wheel so alarm, remote locking etc were all Ok.
(That's not exactly how he described it, but it's about right I think)
Time will tell, If the car starts in the morning then I'll be happy.
10/10 to the RAC man though, didn't try to fob me off, or rush anything, just worked his way through my problem methodically till he was happy with the solution, I've had them in the past that weren't interested and just wanted to get my car on a breakdown wagon and out of their hair.
Are the leads from the battery in good fettle?
Fingers crossed this was the issue.