Don't confuse the performance of an old, and rubbish boiler with a working new one.
Ah, you know that never occurred to me!
When you consider this Icon t23/Glow worm/Travis Perkins special is 11 years old and 8 when it went south that's a pretty valid point!
What's the likely difference between the two types of boiler regarding system pressure, most of the new units are high pressure if I'm reading the various gumpf correctly..