I did it once and also would not do it again. As has been mentioned before the hourly rates need to be higher because 500/year is optimistic at the very least. Your aeroplane will probably be treated as the runt of the family if the school also has their own aeroplanes, guess which one will be the last to fly? If they are responsible for the maintenance it will get the bare minimum and on the other hand if you are responsible for it then you will be blamed for the downtime as a reason for not making the mythical 500 hours. I'd advise against it. Regarding the engine I would assume that a good zeroed engine from a reputable source is going to cost you upwards of £12k plus around £2,500 to remove and replace. Plus of course all the other little bits and pieces that can be sorted while the "big" job is being done......
Beware of the taxman as they will be wanting benfit in kind off you. You will only escape this if either you:
a) never fly it yourself
b) have more than one aircraft owned by the company and available to you (a la pool car)
c) have more than one client for the aircraft.
Even the above will not guarantee immunity. You MUST go and see an accountant who is familiar with this scenario or you could have years of grief. Don't ask me how I know.
