SE England - ideas for day trips / 1-night stays

[Lighttodark]

Thinking of doing day trips trips and mini breaks over the summer holidays rather than a 1-2 week break. Ideas please!

Whitstable
Folkestone
South Downs
Brighton
Castles - Leeds Castle, Dover Castle, Hever

Portsmouth - the naval dockyards & Spinnaker Tower

Hovercraft to the Isle of Wight