Yesterday I got home to find my wife trying to try some clothes on the radiator, but the radiators weren't getting hot. I checked that both the control panel in the airing cupboard and the thermostat in the hallway were calling for heat, then took a look at the boiler.
I took the front panel shield off the boiler, to find just two lights lit (boiler on, fan on), but no pilot and no burner. My first instinct was maybe we've got no gas. A quick check next door sadly ruled that one out. The boiler was humming, but for some reason it wasn't getting as far as lighting the pilot and the burners.
Frantic googling revealed this post amongst a few others. It seems that the boiler won't fire if the fan isn't running, and the noise I could hear was the motor failing to spin the fan.
DISCLAIMER: WHAT YOU DO WITH THE FOLLOWING WORDS IS UP TO YOU. I ACCEPT NO RESPONSIBILITY FOR YOUR ACTIONS, YOU SHOULD PROBABLY PAY SOMEONE WHO KNOWS WHAT THEY'RE DOING.
So, off went the electricity, out came the front two philips screws, off came the casing, off came the four spring clips (2 each side), off came the metal panel.
At the top of the unit there's a fan, which at first glance looks like a fully sealed hairdryer-type assembly, but on closer inspection there's a small spindle on top of it with a number of small silver fan blades. Spinning this with a pencil found several places where it would stick, so I repeatedly squirted copper grease all over the fan spindle, and now it's running fine again (for now).
A bit more googling found that the Solo 2 is only 68% efficient, and therefore G-rated (I've no idea how old it is), so I think it may be time to think about a replacement as it's bound to stop again (probably xmas eve knowing my luck).