Never been to the Lemp specifically but the whole tragic history of that family makes it one of those places I'd expect to feel heavy the moment you walk in. Multiple suicides in the same house, decades apart - that kind of repeated trauma has to leave something behind. I've visited enough old properties in England where the atmosphere just hits you before you've even had a chance to think about it, so I reckon your reaction is probably more genuine than you're giving yourself credit for.
What exactly was the feeling? Was it a specific room or did it follow you around the whole building? I always find that detail matters more than people realise - a localised sensation versus something that moves with you are very different things in my experience.
Would love to hear what others who've actually been there thought. Particularly curious whether anyone picked up on anything near the basement areas.