Cheers TM for taking this on.
Regarding the Peak District, there's lots of speed restrictions across many of the more interesting roads (Snakes Pass, Woodhead Pass, Winnats Pass, Cat and Fiddle run etc.) so it won't offer the progressive stuff that it used to. However there are some lovely, technical single lane and minor roads (Pym Chair, Goyts Valley, Holme Moss, Flash village etc.).
Every time I've ridden there over the last decade the riding has become more disrupted by intermittent speed controls and the approaches to it from the west are peppered with mobile and avg speed cameras.
Some ideas for consideration?
Forest of Bowland - Lake District
North Pennines/Wearhead - Hadrian's Wall (a natural extension of last year's successful Yorkshire Dales with similar thrills on offer?)
Northumberland - Borders - Kielder
Lincolnshire Wolds (doesn't have the beauty of the National Parks but has some cracking, open roads and near to the seaside)
Lyn Peninsula - Anglesey - Snowdonia
I think that we all know that everything south of the Peak District is much more limited and congested (except Wales of course). Even Cornwall and Devon have become a bit of a damp squib for biking...except perhaps the North Devon run and the Exmoor/Dartmoor routes.
I have been playing around with a South West route to pick up on some ancient stuff, viewpoints and picking a way around the major congestion points. PM if you think this is worth investigating.