So here goes with an update
I returned to Hindringham, after seeing a flock of c400 Brents in winter wheat field they have been present on & off during Jan & Feb, but I thought they had gone as I have tried previously without any luck (pretty mega 8-9 miles inland from the coast!) Anyhow I saw them on the 20th whilst with a client, hence I was in the car.
I returned today on the 21st to find they were present, but actually I realised they are not visible from inside my boundary!! Fortunately as I stood scanning the distance, a car driver (whom turned out to be a bit of birder!!) stopped & wanted to know what I was looking at? I sheepishly explained the conundrum & he did his bit, stopping once level with the flock was enough, shall we say to "encourage" them into the air!! Brent Goose 91.............Cheers mate.