I married a Norfolk girl (1 head, 10 toes) and moved from an area with great mountain biking to North/West Norfolk. As above Norfolk has a certain charm, and whilst living in Surrey i had Swinley and Surrey Hills, i also had ridiculous traffic, unfriendly people and a commute on the M25.
There is a surprisingly vibrant MTB scene in Norfolk especially for XC/Endurance racers with Thetford (good off piste in places) Shouldham Warren, Sheringham etc, don’t expect any epic downhill!
For me, i just had to re-adjust, i have to travel outside Norfolk with old mates for brilliant singletrack and hills, but i can ride a road bike or MTB from my door on roads and bridleways and can ride for 50 miles and see 4 cars and a tractor.
I also have the “Best Beach in the UK” at Wells/Holkham up the road so have embraced the fat bike and long rides along the beach.
Only thing i would say, is that Great Yarmouth is a bit of an old seaside town that has seen better days, it is all chips and neck tattoos now, but there are lots of nice towns and villages in the surrounding area and Norwich is nice city.