High volume help

Like many at the moment I don’t have to commute anymore so I’m taking the opportunity to go from MV to HV.

I wanted to check I will get the benefits I want though: normally in longer rides I start to get fatigue/cramps normally at about 45 miles in. I want to improve this ability to endure. Will HV impact this in a positive way?

HV has more Z2 work, that is a bulk of the increased volume which in theory should help you. You didn’t mention the intensity of those 45 mile rides, but in any case long rides in Z2, 3-4+ will help you.