I am wondering if, because Mika is 'top of the bill' on that list, that he is the headline act and so will be on last. That makes a certain sense to me at least (plus a bit of wishful thinking!). Objectively speaking, if I were organising the running order, I would put those acts on in reverse order, ie open with Will Young (established name) and close with Mika (the most flamboyant act).
As for the weather..not looking good is it. I don't have a hat, but I am starting to wish I had; maybe a rain-proof golden balaclava might actually be the wise choice .