What is your main interest? Clocking up miles, spotting/bagging units/locos, taking photos? More interested in freight or passenger workings? Each needs quite a different plan.
I did my ALRs mostly to photograph trains and I found by my third trip that carefully planned advance tickets with some rangers/rovers gave flexibility at a much lower price than the ALR itself.
If you have some set plans in mind, might be worth looking into a combination of local tickets to see if it works out cheaper. You get the plus of seat reservations on the longer stuff and can be flexible with start times and even take a day off. There are some good Scottish rovers for example, see
http://railrover.org/ for more.
Glad to see you want to come and visit us up in Yorkshire. Leeds, Manchester and Sheffield are the hubs for Pacer and TPE 185 action. The Sheffield to Manchester Hope Valley line is by far the most scenic in that area, the Settle and Carlisle is gorgeous too but does take a good few hours to traverse. If you like good scenery, running Leeds to Carlisle and down to Barrow (possibly by 37 LHCS if you time it right) is a full but beautiful day out. If you want a long run on a Pacer at full pelt, the Leeds to Morecambe line is fun, although 150s do also operate these workings.