I can't give you a definitive answer but this was my experience...
Open day was on the 7th of July and there was a listed AD on the 30th-These were the dates listed on the website.
I had already applied to the AD in another country and could not attend so I postponed and applied for the one here as they told me to do, I also sent an email to say that I would like the assessment... Well I did not hear back and the Open Day was coming up so I figured I may as well go...I thought the AD would be on the 8th...it wasn't
The Open Day was a pre-screening for female applicants only and males had a CV drop off. My 'advice' to you is if you are female then go, if you're male---it's up to you....
After the Open Day the Assessment Day was still the 30th... so people whom had come from overseas had to come back for possibly 3 more days.
I hope that has somewhat answered your question... but I guess you'll never know until you try
