Why is my central heating boiler not igniting?

I recently had a new kitchen fitted with new gas appliances where before it was electric. The gas engineer the kitchen company contracted split the gas pipe to the boiler (about 1 meter below the inlet), fitted a 'T' junction to the pipe for the new supply to the hob. Ever since I have noticed the boiler becomming slower and slower to start up, now its not willing to start at all. I had the gas heating contractor back yesterday, He opened out a screw under the gas valve at the inlet side where a hiss was heard, he then opened the screw at the other side and no hiss was heard, he said that its the gas valve thats to blame and that there could also be other assosiated faults like the motherboard being faulty etc etc... . No checks were made to see if the gas pressure was high enough for the boiler. He Said he could replace the valve with no guarantee the other components will work. He also mentioned it probably would be better to go for a new boiler as this one is getting old (almost 10 years now).
The boiler make is an ideal classic fan flued FF240.
Im not sure what the next steps are to take, go ahead with repairs or get another party in to inspect the problem.

Many thanks in advance for any advice