If it has yellow on it I can't see what else it can be other than a siskin. They're only marginally bigger than a blue tit and asterix admits he only saw them once in a tree and is no expert.Rules siskins out. They are bigger than blue tits (and coal tits are even smaller) and they aren't agile like blue tits are. The easiest way to ID a coal tit is look at the back of its head. If it is black with a big white stripe up the middle, it's a coal tit