Seaside day trip from London - where?

[desperatetostaypositive]

Fancy a day at the coast. Don't need a seaside town, just a beach - ideally a bit wild/quietish/for a blast of air and a great walk.

Where would you recommend from North London?

Aldeburgh? Whitstable? How far are you willing to drive?

Southend is the closest to London but Frinton is nicer.

Might be too far but we love going to Blakeney for the seal boat trips and Wells-next-the-sea has a nice beach.