How can I fix my cannon chichester gas cooker?

It made a loud bang whilst cooking my sunday roast now the electrics dont work & I have to ignite it by hand but in the main oven the gas wont come even through to it but it comes through to the small top oven, grill & hobs but Ihave to ignite it with a match! Its a cannon chichester double oven, I've tried the fuse regarding the electrical fault but nothings made any difference, the bottom oven seems to have completely shut down!!! Please can somebody help me?