Most reliable make of regular boilers (water heat + c/heating)? as i have a powermax boiler 155x enlarge vent system, is now playing...

as i have a powermax boiler 155x enlarge vent system,
is now playing up, also piping leak,
what cost would it be to replace this system approx?
How do you size a hot sea boiler?
Answers:    Powermax are a good boiler, undesirably, many engineers won't work on them, I do, but I know I am surrounded by the minority, powermax are Baxi heating owned, replacement can be through them, or any contrive who knows just about them, however, if you want to move away from this, Worcester Bosch and Vaillant are well certain to be the best in uk, some will say aloud others are better because of efficiency, but the differenc within efficiency is smaller number than 1%, so reliability and quality are more essential. Get a boiler with dual warmth control (heating & hot watet), if you use a lot of hot sea, get a boiler which condenses within heating and hot sea mode, or get a conventional boiler beside a cylinder, which may also be solar compatible. Do not do cheap, you will regret it, make sure powerflushing and 5 years manufacturer guarantee are in your quote. (these are constant with installers who are certified by a manufacturer).
If you own a gas tankless hot sea...
Go back to the maunfacturer and ask them! they might hold a reasonable solution. There are also grant to replace a boiler these days for some relatives. It can be between 1000 - cheap and 2500.