Little update:
I rang them up yesterday and told them I will not be returning to clean the windows until my balance starts getting cleared.
Last night I printed out an letter before action and today I sent it special delivery, I got home and then checking emails they have sent me some payments, not all of them but a small amount so they are playing ball now I’ve raised a bit of hell with them yesterday on the phone.
I went back to the post office and got my letter back lol.
I don’t think court will be needed now BUT this hasn’t been a total waste of time because I’m prepared now for if they do decide to try and trip me up.
Thank you all for the help and advice, I feel more comfortable now knowing I know what action to take if any of this comes up again.