I found the A-Z to be a bit cumbersome as it is huge (11" x 15") and I didn't think it had any more detail than ... AA Road Atlas Britain. The AA is 9" x 12" and fairly thick. When I traveled last year I carefully cut out the pages I needed and made a smaller book. This stood up well and the pages are now taped back into the original book. We were traveling from Edinburgh through the border country and down to Yorkshire, including Durham and Whitby.
This year I will be doing that again, but to get more detail I have added The AA road map Wales, since that is where we are going. This has a scale of 4 miles to the inch and provides more detail than the book maps.
I have used OS maps in the past...I navigated while my husband drove. The scale is huge and in a small car it was a bit of a challenge, on the plus side it showed scads of places like standing stones and neolithic sites, castles and such that the other road maps didn't have. It is meant for walking but since we were doing some of that, too, it worked out well. One drawback of the OS maps is they cover only a small area so you have to buy multiples to cover any distance...and they are not cheap.
My husband and I have little trouble when using this combination and our GPS loaded with the Great Britain maps.
Safe Fun travel to you.