Hey,
I wouldn't worry about the video too much, it's not compulsory and to be honest I didn't say much in the video that I hadn't already said in my written application.
The situational judgement test is interesting. I was very certain about some of my responses but with others it was more difficult to decide which of the four options I would be most likely to choose, either because my gut instinct was completely different to the choices given or because I found all of them fairly reasonable and thus it was hard to pick which I thought was best! It's not timed though so you have as long as you need to mull it over. I listened to a podcast that recommended reading about how varied the role of a social worker can be and all the different things they may have to deal with, as this can help you with the test.