I've realised my mistake now, I had already tried what you suggested but now realise that of course the result will match the entire postcode and not just the first 3 letters / numbers. I was curious why when I did a search for NE1 there were no results, and it's because there are no postcodes of just NE1, but many of NE1 XXX.
I've corrected the query and all is fine now. Thanks for your very quick reply. Best extension I've ever used!!