How to fix my Baxi Solo Power flue?

I came home from work last week my house was freezing?? My boiler wasn't on....my wife turned the boiler knob to low then upto high, this started the boiler and the raditors got really REALLY HOT!! The thermo doesn't seem to have any effect and I guess it only now goes off when it over heats. Can anyone help with what the fault may be.....I'm really hot or bl**dy freezing.... HELP!! Please (Baxi - Solo - Power Flue)