Apologies, chaps; my comment on it being for sale was tongue in cheek.
I think this accident was the tip of a large iceberg of dodgy fuelling practices, involving people leaving the UK with minimal fuel, so they get the biggest benefit of the cheaper fuel in the Channel Islands. But surely the benefit of the cheaper fuel is much less than they think, due to the possibility of the UK duty drawback. But to get the maximum DD you want to leave the UK with full tanks! This is safer and avoids a fuel stop in the CI (hassle, time, 12/24hrs police notice required, extra fuel burn in the subsequent climb). I bet that if they worked it out, they wouldn't bother in most cases. I never stop in the CI unless I actually want to stay there a bit. The one exception would be someone, with big tanks, who is based close to the CI (say Plymouth or Exeter) and who flies a lot internationally so he cannot make much use of the DD (the DD allows the duty to be reclaimed just once for each fuel load, obviously). He can then use the CI as his local refuel station. But the 12hr police notice is a hassle so you want to be based at an airport where you don't need to do that.
This Covertry - Guernsey - France flight was completely pointless. A Baron can do Coventry - Biarritz on something like half a fuel load. The TB20 has a 1300nm range (roughly, Coventry to Malaga) and I doubt the Baron is much worse.
One has to wonder about the psychology underneath this.
OTOH, what I would call dodgy fuel practices are not uncommon in twins. This is because every plane allows you to trade payload versus range, and on twins this trade is wider than on most singles. To carry 6 (or even 4) people in a Seneca, you need to depart with fuel way below what can be physically inspected, which is OK if you really know the plane, or have a fuel totaliser fitted which you know nobody could have fiddled with (when I used to rent out the TB20, one renter - an instructor - fiddled with the Shadin to get a smaller fuel invoice; he got caught with the EDM700 downloaded logs which he didn't know about).
So we probably have a lot more people cutting it fine in twins than in singles but OTOH a lot fewer twins are on the rental scene so most are flown by pilots who know them well. G-OMAR (google for the AAIB report) is an absolute classic worst-case where a pilot was renting a twin whose (flying school) previous flight records were dodgy (plus some other factors which didn't help).
If you have a fuel totaliser you can do it precisely but I suspect only a few % of "seriously used" piston planes have them. This I find bizzare because it is relatively cheap to install (a tiny fraction of the 5 digits which some owners dump at some avionics shop for a load of fancy gear which gives them precisely nil new capability or safety) and solves the major issue of dodgy fuel gauges which are the norm and not the exception.