DIY Doctor UK DIY Forums

I would be grateful if anyone could help advise/clear up the following situation for me. I recently (May 2016) had a new Combi Boiler (Vaillant Ecotec 835) fitted to my 3 bed 1.5 bathroom house that has 8 radiators and no other gas appliances by 2 gas engineers who work for a very large (over 130 plumbers) and well known heating contractor in the South East, I should add the work was done on a private basis and not through the well known company.. Over the last 2 months the bar pressure has dropped 3 times where the boiler has cut out, I was unable to contact the 2 gas engineers and assumed this was a fault with the boiler so had a Vaillant engineer out to check the problem. On his inspection he has found that there was maybe 1 or 2 very slow leaks on 2 radiators and that the boiler has a ‘low inlet working pressure of 10mb’. He also found that a new gas pipe of 22mm was NOT installed from the meter to the boiler, it is was just connected to the old pipe at floor level to all of which he has issued me a warning notice and turned my gas off. Can anyone advise how serious this is and whether the 22mm pipe needs to be installed or not as this is all under the new floor/kitchen I had installed? I have tried to contact the 2 gas engineers who installed my boiler without any success and have just noticed that the gas certificate they have given me was signed/completed by an engineer/different company (Corgi Registered) that is neither of them and this 3rd engineer who has completed the certificate was never at my property and yet he has stated my boiler has 22mb on the commissioning paperwork. Have they broken some regulations here, besides not installing the 22mm pipe, they have fraudulently completed the certificate, will informing Corgi do any good? Thanks in advance for your help.