Actually I found out how to do this by right clicking the variable e.g. MeanWSS (under constants per part) and then select plot vs time. Have kept this here incase someone else finds it useful.

It plots the SpaMeaWSS against time, sampling the maximum over time (which appears similar to the minimum over time anyway as it is a constant). Output is below and I have done this for proximal and distal.

One further question, how could I export this value against time to get this for all the timesteps in a single file that I could view in excel. I may have 5-6 cases and could then amalgate and average then to have a generalised comparison of the cases.  Thank you in advance