Just tried and its not working so I'm pretty the motherboard has gone kaput. I've got another old motherboard and cpu so I'll try that to ensure the PSU and/or case isn't to blame.
I brought that board and put it in yesterday. The power buttons on the case wouldn't turn it on so I suspect the buttons on the case have gone bad. I'll take everything out tomorrow and return it for a replacement or different one.
Finally some good news. I took the case back today and the guy tested it but got the same results as me. So I decided to swap the case and went for a Deepcool Tesseract BF instead. Got it home and put everything in and it's working great.