You've got 8 days which is ample if the weather is OK. There's no need to stay on the boat all the time, unless it's your idea of fun which is fair enough. A couple of hundred miles each day followed by a couple of beers and a B&B would be a much better idea!
The route we used in 1999
worked pretty well, although Hull wasn't a particularly good choice. Brian may have better ideas for that part of the country.
As you have probably gathered, petrol is the biggest logistical challenge but I'm sure you'll manage.
Just keep your fingers crossed for some good weather . . .