Screwfix no nonsense heavy duty degreaser. Been using a month or so now for conny roofs and dirty first cleans.
I did an eot a couple of days back with dried on egged windows ............... I really thought I was going to struggle with cold water but stuck some of this diluted in my backpack and left to soak for 5 mins, came up a treat
Best thing ............... no need to be ordering online and waiting for delivery, If I run out or need some in a hurry screwfix is pretty much everywhere , my town has two of them within 10 mins of me