This looks really ambitious! Just a suggestion: don't try to do the entire island of Britain at once, it may be too big to chew. For your own sanity, start with something smaller. I went for Jamaica in my recreations because, in the atlases I used, it's small, with not a lot of roads or towns, so it's not too bad to start. If you start with something small (the Isle of Man looks about the right size) you can get the map style down before you go crazy with thousands and thousands of roads and towns .

Good luck! I'm looking forward to seeing more of this project!