LHA

I live in a 3 bedroom private rental there's myself my partner and 25 year old son who is currently doing an IT apprenticeship I have my own bedroom because of my medical issues so we get the 3 bedroom rate of LHA my landlord is selling up so I've been looking for ages but all 3 bed properties are unaffordable if I moved to a 2 bed property and my partner uses the living room to sleep in would I still get the 3 bedroom rate as this would make properties affordable I'm just worried because I can't seem to find out I've put messages in my UC journal but they don't seem to know if anyone knows the answer please can you let me know thanks in advance .