In some of the more touristic areas you may also find routes signed in brown as 'scenic route' which make for very nice drives. Also, sites of historical or scenic interest are signed in brown. If you are visiting many historical sites, then it may be worth joining the national trust. A years membership may sound like a lot, but you can easily save yourself the membership in a few weeks of concentrated visits and the houses and landscapes they protect have wonderful photographic possibilites. I've found they're usually pretty cool about the use of tripods as well (though not inside properties obviously).
http://www.nationaltrust.org.uk.