Day trip ideas near Harrow

[nothernexposure]

Hi, I'm hoping someone can give me some inspiration! I'm looking for a wheelchair accessible day or afternoon out where I can take an elderly relative and a teenager. Ideally about 45 mins - hour from Harrow. Elderly relative is a bit of a culture buff and enjoyed gardening previously so a NT or English heritage type place would work. More looking to entertain the relative than the teenager! Any suggestions gratefully received

I've not been here - but want to:

www.heathrobinsonmuseum.org/

Ooo, that looks great and the sort of thing they'd love. Unfortunately it looks like it only open Thurs - Sun which sods law isn't one of the days I can visit. I'll definitely keep that for another trip tho