Hi: I'm going to Norwich and flying into Gatwick. Isn't there a Jetlink bus that leaves from Gatwick, like the one that goes from Heathrow to Norwich?

No, but I can't see why the brandname of the bus matters.

There are National Express buses every two hours or so, taking a bit over 5 hours. And more frequently, changing at LHR, STN or central London and taking five and a half or six.

Gatwick is just about the worst place in the world to land at if you want to get to Norwich. The intercontinental airport for Norwich is Amsterdam, which has reasonably regular flights to Norwich. There are a few intercontinental flights into STN, which is the closest serious British airport to Norwich. You might also find convenient connections to Norwich through Dublin or Manchester.

Or, if you are adventurous, you could take the train from Gatwick to Victoria, (about 30 minutes)transfer by tube or cab to Liverpool Street and take a train (about 1.5 hours) to Norwich.

Or, if you are adventurous, you could take the train from Gatwick to Victoria, (about 30 minutes)transfer by tube or cab to Liverpool Street and take a train (about 1.5 hours) to downtown Norwich.

Train would be much quicker - service at least twice hourly from Gatwick to London on Gatwick Express and even more frequently on Thameslink trains to Kings Cross which is a lot closer to Liverpool street station than Victoria (but Gatwick Express trains to Victoria are much faster and much more comfortable and luggage-friendly and also cost quite a bit more).