Can the hospital keep my mother in against her will?

My elderly mother aged 87 was admitted to hospital because the abscess on her leg wasn't healing. She went in for treatment for that but one week later I think my mother is worse off.

She has been totally immobile, either sitting in a chair or lying in bed. My mother has arthritis but despite that she moved around, even going up and downstairs.

I saw a social worker yesterday who said she needs 24 hour care, which I dispute as she didn't need 24 hour care last week. It's only the abscess which is bringing her down.

Can I make a decision to release my mother from hospital as she is really very very unhappy in there, and that is also bringing her down?

Or can the hospital force us to keep her in hospital or moved into a rest home which we (my family) don't want.

Thanks. We live in the UK.