Actually not. This is perfectly feasible, even if your boss pays all the flying costs (not just an even share), even if you only hold a PPL. So it doesn't even have to cost you a penny.
There are a few restrictions through. From memory:
- The flying only needs to be incidental to the trip. In other words, the trip would have been possible, and making sense, without (you) flying. This prevents aerial work being done under these provisions.
- Your boss cannot require/force your co-workers to fly with you. They should have the option of going by another means of transport.
I think there's an AIC, safety sense leaflet or something to this effect from the CAA. Should not be too hard to find.
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Edited: found it.
http://www.caa.co.uk/docs/1428/Summa...INAL9Mar10.pdf
Look at para 6.4 (page 6).