While I will be of little value with advice (have not personally ridden that ACA route) I wanted you to know that you certainly have a "fan" :- ).
On the outside chance that you have not already gotten into your possession and already started studying the ACA maps ....
for speed, here is the link:
... for well updated documentation of most all the various places to stay and re-provision, etc., etc.
After you purchase a map ACA provides an on-line update link so that whatever map revision date you have you can then download last minute updates just before you launch. Updates are sent in by cyclists who travel the routes and then are verified by ACA HQ.
Where topology variation is significant the ACA maps typically include elevation cutaways.
Meanwhile .... I have searched for your UK "Bespoken" brand trailer and found that there are many popular designs ... when you have a chance could you kindly post a link to the one it sounds as though you already plan and/or have already employed in your previous runs ? - Thank you.