Why would China ignore what is a much different relationship between Taiwan and the US? The US absolutely needs Taiwan, at the very least until semiconductor fabs are established domestically. And even then, it's unlikely that TSMC, AIBT, etc. will consider moving their top end fabs (e.g., 2 nm, 1 nm) to the US to ensure long term success. There's also, of course, the fact that nobody wants this in the hands of China because it would put the US years behind china in semiconductor manufacturing, and by extension, defense technology.
Even semis aside, Taiwan is important for supply chains, anchors the US amongst neighboring allies, etc.
I'm sure you considered all this though.
TLDR: If you think China will decide whether to invade Taiwan based on Ukraine, you are a moron
If the UK signed a deal with Ukraine and did not inform Trump, at this point they are no longer an ally.