Well I made it there and back alive!
Thanks everyone for your advice and suggestions, very much appreciated! I must say I was very pleasantly surprised by night cycling.
I found my £60 quid Cat Eyes were more than up to the task of illuminating the road ahead (at least at my somewhat steady 12mph!) which was a nice surprise. In retrospect, +1 for the helmet mounted light - I didn't get one in time, and I agree it would have been useful for spotting signposts et&c.
I set off around 4pm from Newcastle and despite early evening commuter traffic found it a very enjoyable cycle through almost to Darlington, when I took a silly wrong turning and ended up in the back lanes of Stillington Racecourse. In the end I had to knock on some poor chaps door and ask him directions. Very obliging though he was I couldn't help but feel a tad embarrassed.
Had a cuppa in Darlington railway station and set off to Northallerton. Another badly signposted junction (honestly!) had me heading up what felt like a mountainside for six or seven miles before ending up on the Northbound A19. An almost direct backtrack and I found the road to Ripon via Bedale. All in all it cost me about 30 miles.
At Bedale service station I stopped for a break, food and drink, and the very kind attendant bought me a cup of coffee which, considering I hadn't seen a soul for an good hour, I thought very good of him.
From then it was a straight run through Ripon and Harrogate and up to Leeds Bradford Airport, which is a cruel, seemingly endless bank. If I do it again I'd add ten more miles to avoid that bank without a shadow of a doubt.
Despite the weather, which got torrential at times, what a satisfying feeling to eventually arrive in Bradford for breakfast! Very pleased I 'risked' a night cycle, and thanks to everyone for the advice.
Cheers
Andy