OK I accept my mistake and apologize as in the morning today my family needed hot water. So I opened the front panel and see that gas guy didn't even close the screw on the Gas valve inlet pressure test point but luckily I hate turned off the gas at night from the mains. So I closed the screw and tested for leaks by smell and some soap bubbles and there was none. I tested the hot water and it works which wasn't a surprise but the heating came on and stayed on. I put the heating on for whole 1 hour and the boiler was modulating and keeping the temperature set. So now I must question did the gas engineer really had any knowledge at all.
Anyways I will be calling a Biasi engineer who do a one off repair for £225 including all parts and labour and give a guarantee for 3 months on all work done plus 12 months on parts. Although the boiler didn't lock out in DHW but I see that the temperature on the boiler can go to 90 C (even on the minimum setting) which I believe is due to blocked heat exchanger plate. So I was thinking of ordering the part myself and get someone to fit it and get the other cleaned so next time I will have a spare so let me know what you guys think of this. I also would like to thank you for support and valuable advice and I am glad I am still not out of pocket for which would have been more than 400 pounds for the time engineer spent.
Anyways I will be calling a Biasi engineer who do a one off repair for £225 including all parts and labour and give a guarantee for 3 months on all work done plus 12 months on parts. Although the boiler didn't lock out in DHW but I see that the temperature on the boiler can go to 90 C (even on the minimum setting) which I believe is due to blocked heat exchanger plate. So I was thinking of ordering the part myself and get someone to fit it and get the other cleaned so next time I will have a spare so let me know what you guys think of this. I also would like to thank you for support and valuable advice and I am glad I am still not out of pocket for which would have been more than 400 pounds for the time engineer spent.