Just thought I'd bump this one up as I think it would be a great ride.
It has the cachet of being almost a coast-to-coast (Carlisle is a little bit inland) and has main line train connections at each end.
The market square in Carlisle would make an excellent starting point. Main roads to Brampton then some dark, empty lanes to Gilsland then, the best bit, up onto the Military Road. Running alongside the Roman Wall, this has to be one of the most exposed roads in England, with few trees or even corners to shelter from the wind - but it's normally from the west so should be a tailwind. Aside from the wind, its got some lovely sharp dips and some decent climbs, then a long descent back down to the Tyne. It's also got a bit of history to it too, built to defend England against Scottish invasion by enabling the army to get across to Carlisle and make the cover tackle if Bonnie Prince Charlie were to come again.
I don't know the Newcastle end so well, but I expect there will be a suitable cafe in Whitley Bay or somewhere, and there will certainly be Brown Ale - in blue star form.