As promised, a suggested route from Pocklington into York - just shy of 20 miles, fairly flat and virtually all on country lanes.
It's a dead easy route and could be an ideal way to add those extra miles on that might be required?
The only "busy" bit will be a couple of hundred yards or so of the A166 in Stamford Bridge to get across the river - but there is a pedestrian bridge if you don't fancy taking the road bridge.
That said...the route in York is a bit sketchy - I've relied on Garmin Connect to choose a suitable route from NCN 66 (around mile 17) to York Station - I don't know central York too well, especially not on a bike, so happy to be corrected here.
View attachment 403893
Just a suggestion, not a deal breaker if it's used or not.
GPX also attached.