I know there are differences between the USofA and the UK for rehabs. But if you are going to a rehab only hospital, expect to get plenty of rest, except for when they wake you every 4 hours or so to check you vitals etc. If you recall one flew over the cuckoos nest, when MacMurph came shuffling through the room - that will be you for a day or two. They are going to relax you and watch every move you make. You are going to be fed and maybe have some counseling sessions. Probably not a whole lot else.
If you graduate - step down - to a rehab facility then it is a strict schedule of meetings etc. Up early and bed early