I would stick with Evohome if you can. Evohome, OpenTherm and Intergas work well together.
It may be you need to go through the tedious process of wiping everything and starting afresh to ensure any gremlins are cleared out. As you have hot water as part of the system remember when you start to bind again to set up domestic hot water first before anything else. 8 years ago I learned that the hard way! At the the time Richard from the Evohome Shop posted good advice on setting up in this forum which was excellent. Better than the Honeywell Manual.
I changed my boiler last year to an Intergas combi so no more hot water issues. The usual one was the sensor not connecting. That has been much written about elsewhere in this forum.