Thanks for the input all!
Climbing works out about 1800ft in a return, most of the climbing on two hills near the start and end of each the journey, I rode to my physio appointment on the other coast yesterday and while just as hilly most the hills had a good run up so could get a nice run up in the big ring.
The 1st one on the way to work I can take the costal path and it’s a bit easier though the gravel uphill is a bit of work, adds just over a mile as well.
Been using a Garmin Forerunner 230 for a while now never really know what to do with the numbers and my HR shoots up pretty high quickly but drops back down just as fast after exercise.
I’m running 10 speed, I did look at putting a 36 in with a SRAM MTB rear mech as AFAIK the shifters have the same pull.