Just because I've been there and done it doesn't mean that you can. You know your limitations, I don't, so if you go there it is at your own risk. By mentioning the place I'm not suggesting that you go there.
Bodelva, Cornwall, PL24 2SG
"Now the Lord God had planted a garden in the east, in Eden; and there he put the man he had formed. The Lord God made all kinds of trees grow out of the ground—trees that were pleasing to the eye and good for food." Genesis 2 verse 8-9
They've made the Eden Project accessible for people using wheelchairs, self-propelled or powered, or mobility scooters, all of which are available for hire, I borrowed a power chair. The Eden Project is obviously designed over many levels, it is after all a former quarry, but there is a lift near the Visitor Centre down to the biomes, and the pathways are smooth. The powered wheelchair I borrowed, for free, was easily able to handle the slope down through the outdoor gardens. The Countryside Mobility charity have provided the Eden Project with an all-terrain Tramper now, which should make things even easier. I stayed at the Youth Hostel at the Eden Project, which was adequate.