Old Cruser and all. Firstly I am not too sure on the new market hall myself but this thread is about the access toilets.
I have designed many toilets with disabled access myself and as a designer / architect we have to follow strict rules when designing and there is not much scope to make it better.
Have a look at Approved Document M - Access to and Use of Buildings. I would put money on it they comply to the standards.
I am not saying they cant be improved upon
http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partm/approvedAs for the door its a simple turn of the knob to alter the strength, I would guess as its been used its drifted out of tolerance slightly. Again these doors need to shut as now they are fire doors.
I hope this provides more information to make an informed complaint.