I wasn't getting an IP address, no refreshes/renewals/reboots would do it. The only software I had changed had been Avast! so that was removed and I rebooted but still no internet! Grrr... So into the device manager to reinstall the network device in question (Intel wireless card) and there were many unhappy looking network adapters with the name - avast! at the end of them... Why these weren't removed when I uninstalled the software I do not know but they were all binned, then the real network device removed and reinstalled. and hooray, back online!
All with the backdrop of grumpy children, a short deadline and wind and rain outside I was feeling pretty grumpy but this experience has really put me off Avast! So beware ye landlubbers, this 'ere antivirus package might not be the most friendly for Windows 8 users! (I'll try a few more when I'm feeling less stressed).