Lucy, Angus is asking to go sit on the toilet. Sometimes he wees other times he wants to get straight off again before there is a chance of anything falling in there.
From going through a hard time with Mason I'm sure the best thing to do is sit her on when she asks, talk to her and read a book if you've got time, to get her used to sitting. I think it's hard for them to get used to the sitting.
If something happens then you shower her with praise and even a tasty treat if that works for her. Mason loved a little chock bit and after a while I "forgot" to buy some more so he forgot about the chockie reward but was in the habit by then anyway.
Good luck