Error of our ways
Essel
The CAA will almost certainly write to you asking for your report on the incident. That is your opportunity to explain why things went wrong and also remember it is your opportunity to explain what you have/are doing to prevent such a circumstance happening again.
You should consider; What could you have done better to prevent the airspace infringement following the vacumn failure? What were the actual consequences of the vacumn failure that would have had a bearing on your flight? What checks should you have carried out? Should you have informed the FIS, that you were receiving at the time, of your intention to divert? What benefits could you have availed yourself of by informing the FIS of your problem and intentions? You are quite right that a pan would most likely have not been necessary but a problem shared is a problem halved. In other words what were the real priorities at the time and how would you deal with a similar situation next time!
The CAA will be content to know that you have thought the events through and have resolved the matter yourself. The CAA current policy is NOT to proscecute when the pilot clearly has simply made a mistake and that you, the pilot, also wish to learn from the event.