No they don't take into account the value of the house. It is based on income & savings. There should be details on the income or savings limits for your area on your council website.
If you own your own home the debt becomes a charge on your house. Ours is there for 10 years. This means if we sell the house within the 10 years then we need to pay back all or some (depending on the length of time) of the disabled facilities grant. I imagine this is to stop people getting adaptations done, move house & then expect them done again. It seems quite reasonable to me. Having got the house adapted we have no intention of moving!