Weekend camping near London

[mybabywakesupsinging]

Just thinking ahead for the summer really (wistful)...
We got a tent last autumn, there are 4 of us - me and DH, then ds1 will be 5 and ds2 3 in the summer. I can sometimes get out of work early on a Friday and wondered if anyone had recommendations for weekend camping within a few hours of London? I know the kids would like the beach but not essential.
We are on the north side of London- Norfolk coast looks lovely but is a long way for a weekend (am afraid of putting up tent in the dark!)
Does anyone have any recommendations on Essex coast? or Thanet? or maybe I should just look for a nice site inland...
thank you for any ideas...

we've used a Hurley campsite on the Thames near Henley a couple of times - its only 1/2 hour from home and so relaxing!

lovely walks and fields for the kids to play, pluus you can paddle/swim in the river.

close enough for a visit to Windsor for Legoland or the castle if you fancy .

worth a go - but not as exciting maybe as eth seaside!

Legoland would be very exciting though - my FIL has bought tickets which we can use any day next year as his present to the children. They don't know where they are going yet, just that Grandad has bought a special day out in the summer.
They are so small that any camping is exciting!