I think this question depends a bit on the detail facts.
If for instance you are doing an aerial survey over the IOW, take off from your base, fly to over IOW, survey, and fly home. I don't see how you could credibly say that the initial and final stages of the flight where not aerial work when the survey part clearly was.
On the otherhand, if there is a positioning flight to Bembridge, a flight to undertake the Survey ending at Sandown and then a return positioning flight to XYZ, Only the actual Survey flight need be aerial work.
However, if the bill to the customer said,
1 - Positioning XYZ - Bembridge - £1000
2 - Survey - £2500
3 - Positioning back to XYZ £1000
Then all three flights clearly have been aerial work, as there is a clear documented payment associated with each one.