From Winslow 147 miles I’d go via Swanbourne, post office there has seating for coffee and a pastry. Then via Stewkley, Great and Little Brickhill to Woburn. Then go through Woburn deer park, Tingrith, Harlington then Sundon or Sharpenhoe Clappers to Streately to join your existing routing. You’ll like Lilley Bottom, lovely bit of road. Lots of Red Kites about.
Emily’s in Whitwell at 182 miles is a lovely cafe and also bike mechanic there, or Spokes another cafe and bike place, Codicote at 186 miles. 189 miles Woolmer Green, I’d continue on to Datchworth Green (another cafe there) then turn right for Bulls Green. Nothing wrong with existing lane in your route, just it is narrow slightly uphill (the way you’re going) and the winter has not (and still isn’t!) been kind to it. I usually go the other way, if I use that lane. 194 miles, Stapleford, I go right and immediate left, continue till you hit t junction then left on Sacombe road. Road in better condition and heath you pass nice stop for picnic. Plus easier navigation.