If you don't like the weather ahead, a 180 is always a good option.
I've never yet been refused a transit of CAS when weather was a problem.
I've also not been refused a transit of Stansted in something close to ten years. They used to refuse, but I don't think they do so now unless traffic is very heavy. If I can't get a call in on Essex Radar within a couple of minutes, I know to route around.