These aren't actual oxymorons, just some funny signs.

Message on a leaflet:
If you cannot read, this leaflet will tell you how to get lessons.

Sign in a London department store:
Bargain basement upstairs.

Outside a disco:
Smarts is the most exclusive disco in town. Everyone welcome.

Sign outside a new town hall which was to be opened by the Prince of Wales:
The town hall is closed until opening. It will remain closed after being opened.
Open tomorrow.

Spotted in a safari park:
Elephants please stay in your car .

Notice in a dry cleaner's window:
Anyone leaving their garments here for More than 30 days will be disposed of.

Sign in a Laundromat:
Automatic washing machines, please remove all your clothes when the light goes out.

In an office:
Would the person who took the step ladder yesterday please bring it back or further steps will be taken.

Spotted in a toilet in a London office block:
Toilet out of order. Please use floor below.