The last time I was involved in paper maps for field registration...
...what ended up happening were very long lines at the local Ordinance Survey offices trying to purchase the relevant maps to send off as the deadline approached.
You could not use any of the popular and readily available scales, you had to use the 1 to 10,000 scale (about 6 inches to the mile) which show field boundaries, and which were only available in person from an OS local office. The queues were incredible. I spent over 8 hours in one trying to get three sheets for my father-in-law's farm.
That was some time ago, but it was a real pain. I hope that what they've introduced is better now, because I understand that the OS local offices are no longer there!