Mac Air public Wifi

Hi,

I have begun to have a problem connecting to a public/coffee shop wifi with my MacAir.

Other devices work (iPhone/ipad)

It used to work.

Works fine at home (thank god).

There was/is no password just a connect screen (aka Starbucks).

I get the self assigned ip address and no connection

Have tried re-boots, deleting network from know list. Renewing DCHP. Deleting stuff from library and re-booting. Diagnostics is no help. Apple support thing no help.

So frustrating..

Obviously can't reboot router etc, or ask the Barista for their ISP settings..

Any ideas?

Many Thanks