Did a bit of poking around on t'Internet and I think I've cracked it.
Gas supply was working fine with the cooker so I was pretty sure it
wasn't that. No meter or anything.
It said on the instructions to turn off the electricity supply to the
boiler so to be sure I turned off all the leccy. I then scraped around
the pilot light gas feed to see if it was blocked with a pin.
I had tried turning off the boiler but hadn't tried turning ALL the
electricity off before so I am not sure whether it was my fiddling with
the pin or the fact that I turned absolutely everything off that did
I pressed the pilot light gas thingy in and could hear gas (whereas I
could not before). Took a while to spark it but it eventually caught.
Turned on all the electricity again, set the heating etc and all
appears to be ok.
Thanks for the help and fingers crossed!