Every time I go to the Peak District on a weekend there's a camera van camped just over the crest of a long straight on the A57 next to Ladybower reservoir enforcing the ridiculous 50mph limit. There's sometimes a traffic car with it just in case the you decide to stop and hide your number plate/perform a U-turn.
Elsewhere, there's ridiculous speed limits on wide open country road with excellent visibility and the traffics horrendous unless you stick to tiny back roads (which are good, but sometimes it's nice to enjoy a fast, twisty A-road).
My advice - stay north of the M62 or head into Wales