Well I guess it may well roost in the same bush for a while.
It was in the bushes not far from the furthest car park. If you set off along the western sea wall, ie out towards the sea on the path immediately by the cars, then stop about halfway towards the seats/viewing area, and look left into the middle there are many tall bushes. It was near the top of one of the highest of those. Very well camouflaged though, and difficult to describe its position more precisely!
You wouldn't have seen it from the tarmaced path alongside the motorway, even though that may actually be a little closer as it goes behind the bushes.
Then go a little further out and turn round and look at the avocets behind you on the mud flats if the tide is right!
K.