Leaving it rebel guarantees faction re-emergence. So does abandoning to revolt.
Yeah, I suppose you're right...sigh. Thing is, I've got more important things to do, such as invading Italy and expanding the Empire eastwards, and bottling up Spain by taking Navarre and Aragon. I get minimal points for taking the provinces, and risk wholesale rebellion anyway, unless I put some very large garrisons in place.
I guess my point was, if I raid every British province and wipe everything out then I get loads of money and any faction re-emergence has to start with no buildings at all. It'd take ages for them to get anywhere technologically and militarily, I'd only need to garrison Flanders, and my fleets would control the seas around Britain as well. I was also hoping that any English faction re-emergence would allow me to ally with them and marry off some heirs...