totally concur with FF
but just be aware that there are several disused WWII aerodromes between Brentwood and Norwich that can all begin to look very similar.
Another mast that sticks out is Sudbury and there are a couple of lower ones north of Colchester near Harwich.
On a good vis day it will be a peice of ease (if you keep the sea to your right whilst hdg north - you won't be too far out of "zone" - when you start to head west and the sea is on your right then Norwich is south of you.
Norwich City itself can be quite hard to see in poor vis (esp if the sun is very low) so I would suggest that you aim to arrive late morning to mid afternoon to give yourself the best chance if it is a little cloudy over Norfolk.
The Eye power station that FF refers to pours out copious amounts of white smoke/water vapour and is situated on the side of an old disused 'drome just a few miles north of Mendlesham mast.
Even if the viz is not perfect - hdg and time to run should be more than adequate. I'm VERY familiar with this area so feel free to contact me off list if you need more data.
Sizewell (FF's Leiston power station) looks like a huge golfball on the coast - do not mistake the sugar beet factory (white smoke!!) at Loddon, just north of Bungay for Eye. Not impossible to do if you are 15 miles away and can see the smoke but pretty hard to do close up!
During the week there is a lot of low level mil traffic (rotary and FJ) so a chat with Norwich App early on is a good idea.
Have fun, you will enjoy it!