You're not gonna like this reply

. 155 is not necessarily high.
I suggest you take the 220bpm - your age = as a starting point. Mine should be about 168 from that but I've never managed more than 155. The highest average for more than 30 minutes I've had was iirc 145. That hurt, a lot.
You need to determine your max hr. I would suggest a treadmill test at a local gym to give you a guide. I had to do one at a hospital when I was very, very unfit and a smoker, damn near collapsed just walking quickly. Not a good feeling. Or you could try the ftp test and then spend another 10 minutes on the velodrome in zone 5 or 6 to try to max out your heart rate




.
Once you have your max you can work out your hr zones and use them as a guide with the workouts.
Then the pain really begins
@TurboTommy and I are using the Scosche Rhythm + (I've had mine for about 18 months now). It tracks the same as many out there from my experience (I have a garmin, garmin run both part of bundles that I managed to get discount on and also a Wahoo tickr and tickrX). My Fenix 3 HR also gives the same numbers within a beat or 2.
Read a review from this link and then find the sites discount code for Clever Training and save 10%.
https://www.dcrainmaker.com/2014/05/scosche-antbluetooth-optical.html