2006 Polo Mark IV FL - ESP issue

ESP dash button light plus instrument panel warning light illuminate simultaneously and remain on.

Has happened three times in past two days.

First time on motorway, dry surface, 65mph, pulled onto shoulder and tried to activate/deactivate using ESP button, but to no effect. Turned engine off then started up and all ok again. (ESP button then functioned as normal).

Second time, same scenario but as coasted onto shoulder down to 5mph both lights went out by themselves; resumed journey.

Third time was doing 30mph and again once the engine was switched off/on all ok.

Have read elsewhere that this can be due to; a duff fuse, the ABS pump dying or under inflated tyres. Two of these are easy to fix, one is v.expensive...

Anyone with experience of this?