Trapped in a tenancy I never lived in – coerced by controlling co-tenant while grieving miscarriage – do I have a legal case?

Hi all, I really need help and advice on a distressing situation.

Location: Manchester, Uk

I signed a joint tenancy agreement in Manchester, UK. At the time of signing, I was going through a planned miscarriage and being treated for pneumonia. I was extremely vulnerable and hadn’t worked in over a month. Despite this, my co-tenant pressured me heavily into signing the tenancy. He insisted I come collect the keys, and I have text evidence of my hesitation and his coercion.

I was issued no working fob, meaning I never legally or physically took possession. I’ve never lived in the flat or spent a night there. The property was misrepresented (no walk-in wardrobe as advertised), and the balcony was covered in bird faeces — clearly uninhabitable.

Since signing:

My co-tenant filled my bedroom with his belongings without my consent.
He created an unsafe, hostile environment (filthy shared spaces, aggressive behaviour during viewings, slammed doors to sabotage re-lets).
I raised these concerns with the agents, but they say it’s “a private matter”.
Urban Splash refuse to release me from the tenancy or refund my rent and deposit. They say I must find a replacement tenant.
I’ve initiated a Subject Access Request after learning the agent and co-tenant may have been communicating behind my back. I’m also preparing to meet with the property director next week and would like legal backing.

My questions:
Do I have a legal case based on coercion, misrepresentation, or failure to grant access (i.e. the tenancy never properly commenced)?
Could I argue for constructive eviction, harassment, or duress in court?
Is it worth paying for a solicitor to write a letter now, before escalating further?
Are there any legal aid or low-cost services that help in cases like this?
I’m devastated, out of pocket, and feel completely trapped. Any help or guidance would be deeply appreciated.