Hello Pete, We've been having a similar problem ( I think the same code but it's not my job) with a focus c-max 2.0 hdi engine. It cuts out (usually going up a hill) when the fuel level is below half a tank. The fuel pick-up is in a cup & the return comes into the cup around the outside to prevent air being picked up. There is a small hole in the bottom of the cup to keep it filled & to act as a baffle. Above half a tank the cup fills from the top. We've decided the hole in the bottom is too small (although its been fine for over 100k) so probably injectors are spraying more than they should but runs fine & clean. May well be totally different from yours but thought it worth mentioning.