Here's a gigantic blank map template of the full British Isles, as well as an RM adaption. NO random junk, whatsoever. Completely designer-friendly as well.
This should be very, very accurate, as I spent a good deal of time on this and used an atlas.
Feel free to use the template in your works, that's what I made it for. Just credit me if you use the map.
Updated* - Here I've added elevation, as well as I've thinned out random junk. This isn't the easiest thing to do, as this IS on a gigantic map. Nevertheless, more accurate overall and more usefull for you.
Updated2.0* - NO random junk on blank template, as well as dockable waters. A Heptarchy style RM adaption is included.