After trying & failing to get hold of the marina manager in Peterhead, I decided to go with what I thought was about fifty hours of fuel on board (I can carry about four days). We left the marina at 09:35.
On the first day (Thursday) we used the engine for 4 hours. At 23:40 we were getting too little wind to sail, and switched it on again. It was switched off again at 18:15 on the 7th. Total so far, about 46 hours. We had 10 hours left in the main tank, which I thought we should keep for final approach and manoeuvring.
I had drained the reserve from full, getting 39 hours - a useful statistic. I then switched tanks, bled the diesel, and switched it off again.
We were utterly becalmed until 03:00 on the 8th (Saturday morning), so we lost 9 hours because of the fuel shortage. We then sailed towards the channel between Terschelling and Vlieland. The winds were very light, and we were slow - the spinnaker was up for about 8 hours from 09:30g.
At 17:30 we put the engine back on to motor for the last six hours, tying up in Vlieland just before midnight.
In the interim, Carrie had become concerned about our late arrival, and had asked the coastguard if they had heard from us. This resulted in a Pan Pan and a Navtex report, so we were much better known than we expected to be by the time we arrived. I hadn't seen the Navtex report because I had only looked at weather forecasts ...
I should have been much clearer about the range of possibilities.
And I should have been more careful about fuel ...
We stayed two nights in Vlieland, recovering and sightseeing, and filling the tanks, before moving on to Terschelling for a night.