Glow plug light started flashing,brake lights work fine. only had the brake light switch replaced about 2 weeks ago. Any ideas? It's a 2005 fabia vrs.

Are the glow plugs working?

The most common fault is the brake light switch, I know you say you have replaced this but have you checked the brake lights are actually working?

If they are then it is just a generic light showing there is a fault somewhere and only a DTC scan is going to pinpoint it.

Is the engine light also on?

Left it for a few hours, got back in, still flashing, gave the brake pedal a couple of pumps, and the light disappeared. guessing it was just a glitch