The visitors pontoon appears to be fully available again (both sides) as the wind farm craft are now on the eastern side of the harbour. Facilities however remain basic.

I reviewed these notes in early May of 2022. I've updated prices but this place has little to recommend itself to the cruising sailor. The Port Authority can't get its hands on the West bank because of a 999 year lease so it's doing the best it can with the East bank.

...was many things, but never First Lord of the Admiralty. He was famously Secretary of the Admiralty and also a Member of Parliament, President of the Royal Society and held several other public offices. As Secretary of the Admiralty he did his best to eliminate the widespread corruption amongst the Naval administration at the time, instituted many reforms and laid much of the foundation of the modern Royal Navy. Of his work on hydrographic matters I know nothing.

Don't know if it is any help but I've found this
https://www.bodc.ac.uk/european_sea_level_data/sea_level_network/documents/newhaven.pdf

These notes were reviewed in March 2021. There are new prices and you need to check with them for Covid restrictions. The situation with the visitors berths has not changed; it's still first come first served and the wind farm people still have permanent use of the inside berths on what was the visitor's pontoon

For small craft sailing vessels, given that the nearest ports of refuge are about 2hrs away - Brighton to the west and Eastbourne to the east - have found it disappointing that the marina can only give visitor berth availability as you ‘are on your way, call us on the phone when close to Newhaven’. I visit friends in Newhaven (by road) regularly and have only ever seen 0 to 2 boats on the visitors pontoon. Many of the wind farm service vessels seem to park on the east side of the channel.

I am trying to find evidence that the Newhaven tide gauge was originally sited at the Harbour entrance by Samuel Pepys when he was First Lord of the Admiralty. Pepys was a great organiser, but not a good sailor. It is evident that he went about the business of creating the first accurate admiralty charts with zeal. In order to chart sea depths and tide times he needed a reliable tide gauge at a seaport near the meridian that was not in the Thames Estuary. Newhaven was the shortest horseback ride from London and fitted the requirements needed to establish Chart Datum. If he actually chose Newhaven for this project, we have here a unique historical site. from charting the UK waters, land heights above mean sea level could be accurately measured and mapped. When Clive went to India, he was accompanied by an army of surveyors who mapped the whole of the sub-continent from a similar chart datum. Similar surveys were made in the Americas.
I would welcome information and comments. Here.

There is a harbour development proposal which has been agreed by the Ports Authority, but not yet ratified by E Sussex CC and the Road transport Authorities. Proposal is to build a large Ready Mix concrete plant at the Harbour mouth on the Eastern Shore. It will extend seawards along the Eastern pier cutting most of it away to form a ship dock. The pier will be made solid (skeleton construction at present) and backed by a large area of imported boulders on the Seaford Bay side for protection against waves.
Tidal flows at the harbour mouth will alter considerably. From 40 minutes before high tide to three hours after high tide the tidal sweep around Seaford bay is East to West flowing past the East Pier tide gauge at a maximum of 2.3 knots. this will change to about 4 knots with a seaward drift away from the river mouth. The harbour bar will move seawards by about 50 metres from it's present location which is about 5 metres seaward of the western buttress at the harbour entrance. There will also be new underwater eddies when entering the harbour on the starboard lane.
Apart from the unsightliness of this eyesore projecting with high level conveyor belts and 80 foot high silos.

The comments of our members below have been noted. Having had a long conversation with the marina we came to the conclusion that, although Newhaven is not officially closed to visitors, it might as well be while they milk the cash cow of the windfarm stuff.

Towards the end of a round uk trip we thought we would drop in to Newhaven, on the way to Ramsgate. I was told that the visitors berth is now fully occupied by windfarm boats, and they could only take a single yacht , but could not guarantee a berth . One birth is no use - Newhaven is now effectively closed to visitors- the windfarms have won again!

This has now been added to the body of the text above