im done with my tb test last wednesday.
first thing you need to do is to call them for appointment,need patient because it takes time to pick up the phone,not sure why.mine it took 15 mins before they picked up the phone..

once you get there the security guard will give you a number,just keep it and wait your no.to be called.
dont forget to bring your passport and one valid id.

with my experienced it took 4 and half hours to finished,from verification,take picture,xray oh by the way the waiting time is too long,and then you need to go back to 15thf after, to wait again your result.good thing mine is normal.and you can have your certificate on the same day.just check your cert.before you leave coz in your cert it should on it your husband/fiancee adress in uk,my friend gladz also a member here having a problem about it coz she didnt noticed that her husband adress in uk not on her cert.so she keep trying to ring up iom..

hope this one helps to those are about to take the tb test.