went to the openday in december.
came away with the impression that i would be offered an interview if i met all the basic criteria. Personally i went there in advance i.e before IR and licence issue so i've not followed it up since but it's worth it.
you at least meet the people who are going to potentially interview you and get all their contact details. They said upon meeting the criteria you first get called for an interview/chat and if successful get invited to the assessment day that you have to pay for. Not sure if it speeds up the process of selection over and above people who have applied online and not gone to the openday though.