Appreciate your concern but don't see any problem with the gas pipe whatsoever. 22mm to 15mm very standard. Vailla r has 15mm connection which means I always reduce below the boiler. Flow needs another clip? For 1m of flue? I think that's a little over the top though. Everything is safe and secure installed. What you mean with the mac? How is that not safe ? Nothing is going to happen and if the prv opens it's going safely into the waste pipe. No lagging due to price cant do all for peanuts. Not many people are committed to pay for all materials.
Is there any positive word from you rather than just pointing out? Perhaps you show some of your installs. I don't mind and appreciate your opinion as mentioned above. But give also some positive feedback that would be much appreciated too.
I don't think I did anything wrong. I'm happy with my boiler swap