Picked up enough stars to progress a bit further today. So much further, in fact, that I managed to get the remaining three keys and unlock the entrance to Bowser’s Castle.
And met Bowser. Now, I know how to actually beat him (you wind cogs to raise Thwomps which you then drop by hitting a switch and then Bowser falls over and you hit him), it’s just that every so often Bowser jumps up and down, stunning your flippers to you can’t use them. So the ball goes down the “drain” and you have to start again. Gah.