Northumberland 250

I did this a couple of years ago. Great route even goes into southern Scotland. It was also nearer 300 miles (I think).
I chose a time when we had a window of high pressure and nice sunny weather in June and just took my tent. There's plenty of camp sites about I didn't book anything, I just rode until late  afternoon and got my phone out to search for a camp site close. Nice leisurely ride over a couple of days.