A nice ride for the SE, keep your eye out for the old bill tho, especially across Romney Marshes... and great fish and chips in Hastings.
A decent enough route along the sea. Quite windy, as its pretty open.
Another option: from Brenzett, turn off the A259 and take the signposts to Appledore, and then Rye. This will take you along a B road for a while which is OK, but from Appledore to Rye follows the Royal Military Canal, which means four or five predictable "chicanes" on a fairly quiet road with a good surface. Also some longer straight sections with good visibility and little traffic. This brings you into Rye, where you can rejoin the A259. Police presence on the Sussex section of this road is, in my experience, quite high on sunny weekends in the summer.
Instead of staying on the main A259 after New Romney branch left after the bends as you leave the town (signposted Lydd) as you enter Lydd follow the signs for Camber. This route takes you around the back of Lydd Army Ranges - lovely sweeping bends out to Camber where you can rejoin the road for Rye. It's more interesting than going through Old Romney and Brookland.
Nice open road by the sea. Watch out for Police and tourist traffic. Best to avoid peak holiday times as traffic volume can be high. Woolpack pub in Rye recommended for bikers