Not having been in paid employment for over 2 years, I'm not in a position to splash the cash right now. Up until recently we had a reasonable maintenance contract with the installers, so the unreliability was more of an inconvenience rather than a cost. I think a single system boiler (30-40 kW) with weather compensation is the way to go. I may have to wait a little while for another breakdown to justify it.If you have a crib so large that you need the equivalent of 50 1kw bars of a fire burning bright all round the house, then you have sufficient money to get those off the wall and replace them with a pair of ~15kw qaulity boilers or a single ~30kw boiler.
If you can't afford to change the boilers then while they are both running get a service contract.