Wolf, having experienced similar, please take my advice and ask for help via your GP. This is not because you 'are ill' therefore to blame in any way - it is because these people have had a severe impact on your mental and physical health. At the very least you need someone to talk to, some kind of counselling, to help you recover.
Sadly British industry and commerce is rife with bullying and agencies that are meant to support victims seem toothless.
Proving anything legally against these people is totally dependent on other workplace witnesses being prepared to speak out on the record - and much as colleagues may like you, they get all shy when this kind of request is made.
Part of your process of healing will be coming to an indifference towards the liars that harmed you, and this will take a huge amount of time and work.
Moving on in the right way heals. The bullies will be lying and manipulating even in their care homes.
Will you keep us posted about how you're doing? Letting go of a pain this big is a serious process and is IMO as hard as recovering from a diagnosed serious illness.