I know very little about combination boilers but I do trust our plumber so when we needed a new combination boiler I was happy to go with his suggestion. He suggest the boiler he installs for most of his customers, a Heatline boiler. They come in lots of models and because we have a small house, we got a small boilder, it wasn't very expensive, however it does do the job very well.The model we have has a simple timeclock for central heating, auto-ignition, and two dials to alter the temperature of the hot water and central heating, you can connect a thermostat to it and its pretty quiet and if you use the hotwater when the central heating is running it simply cuts out the central heating to let the hot water run.What made this boiler so special was the warranty, it was 2 years and I have personal experience of their service and so does my Auntie.In January we noticed the boilers hot water wasn't heating very well, I phoned up heatline customer service and an engineer came the next day, yes I did say the next day, very quick, very quick indeed.The problem seems to relate to something that can happen with many of the lower specification combination boilers, put simply I live in London and we have very powerful cold water pressure, this means that we have a very powerful hot water pressure, this is great, however during the winter months the mains cold water gets colder and at such higher pressure the poor boiler simply couldn't heat it all up, the engineer reduced the flow a bit, and we now have very hot water again, it's great service from a great boiler.
My Auntie phoned up because there was a smell of gas coming out of the flue, the engineer came out the same day and fixed the problem, again superb service. I am sure all boilers alas have problems, but this free 2 year warranty is great with amazing service, makes this a super best buy for me.