EIG

Yes I agree, I cleaned the contacts well, it was more than likely a high resistance at the bulb contacts.

Sorted - I removed the bulbs from both tail light clusters and tested them with the multimeter, I then reinstalled them and hey presto - the dash bulb now goes out when the brake pedal is pressed. Thanks to all for your help.

No, all the lights are standard fitment.

The bulb failure warning light on my 2005 MK2 stays on permanently. Even when the lights are not on it stays on. All the external bulbs are OK. Any suggestions please.