Some employment claims are fairly black and white, like has the person been paid what they should have been, have they been given enough holiday, or the correct notice period.
But most employment claims are involving issues, and then they often become largely about reasonable behaviour, which is a lot greyer. For the best chance of succeeding in a claim, an employee needs to demonstrate as clearly as possible that their employer behaved unreasonably in the circumstances, which is far easier to do if the employee can simultaneously demonstrate that they themselves behaved reasonably. Otherwise it can just look like mudslinging on both parts.
Reasonable behaviour from an employee in your circumstances OP would be cooperating with any attempt made to get you back to work, including adjustments made to try and address your concerns, suggesting adjustments if there is something you think may help which they have not thought of, and, if you feel they have done something wrong/not done something they should have done, given them reasonable opportunity to put that right, which would normally involve an internal grievance.
Reasonable behaviour from an employer would be making reasonable adjustments to help the employer back to work, listening to suggestions from the employee, and medical advice where appropriate, and in the event of a grievance, listening carefully to the concerns raised and addressing them if possible.
The worst thing someone can do for you is to advise you that you have a claim if you don't, so for that reason it is essential when you talk to someone for advice, that you are absolutely clear about everything that had happened, including anything you think your employer will say that you have done "wrong".
ACAS isn't the best source of advice IMO as they can be inaccurate and inconsistent, but it will give you an opportunity to talk to someone properly about the situation.