I have an Evohome system and all my radiators have Hr92’s on them including my bathroom towel rad and smiths plinth heater.I phoned the Evohome shop and spoke to Richard,the owner who advised me on what I needed.On the smiths plinth heater I have a Valencia straight valve with a Hr92 fitted this just the opening and closing and a Honeywell T87RF2033 room stat controlling the room temperature linked to the Evohome controller,this all works perfectly as per Richards advice.The only thing is you have to make sure that there is either a bypass built in to your boiler for when all the Hr92 close and the water has somewhere to go or an external bypass if your boiler doesn’t have one.I know this is a bit off topic because it was valve adapters that were being asked about,however I thought I’d share some info as I have a bathroom towel rad and plinth heater,it all works as it should and every room is zoned.My system is also Opentherm with a Vaillant Ecotec plus 831 combi boiler using the Vaillant Vr33 opentherm adapter which works very well.