The location is the salt marsh at Brean Down Farm As you approach the farm you will see the sea wall and salt marsh in front of you to the right of the lane/road.
The twite - I have most often seen them in the first area of salt marsh in front of the farmhouse. They feed amongst the grass and are difficult to see well but they seem to like the bushes in front of the farmhouse and when resting there you get get some great views with the light behind you. But they have also been seen up near the old trailers - on the fence at the top of the sea wall and also feeding around the puddles towards the cattle sheds. The twite are almost always in a group of 3 or 4.
As for the Lap - I have only seen it once and it was on the fence referred to above. Others may have better info.