potterton neataheat 10-16 boiler?

hello i have a potterton neataheat 10-16 boiler does any one know where i can get a booklet from i have already tried comp potterton also when boiler on the pilot light comes on but as it tries to light the gas it keeps switching constantly off and on
i bought a gas valve but boiler still is not working can someone please advise me of other options to try, thank you