This thread set me thinking as I seem to detect a worrying and subtly casual attitude to flying out of sight of the surface in some responses. If I have mis-interpreted, then in PPRnNe tradition I am sure someone will admonish me.
1. If you get a vacuum or electrical failure in IMC and you do not have a backup source of either then, IMHO, that is an emergency. You need to tell someone fast and land as soon as possible, with all the monitoring and assistance you can muster. To do otherwise is certainly dicing with possible disaster.
2. Similarly, if you plan to fly or reasonably expect to fly in IMC (or at night) do not accept an aircraft with either power source in unserviceable condition. This is what pre-flight checks are for.
A few years back there was fatal accident where the pilot took off in a C15X with a known unserviceable turn coordinator and ended up (unintentionally) in IMC at night and then lost his only vacuum pump ...
3. There is nothing particularly difficult with flying in IMC if you have the appropriate training and experience, but you do have radar coverage don't you ? I understand there has never been a midair collision in IMC in UK airspace. We need to keep it that way.