Cheers for the info. Unfortunately it didn't fix it.

However we've come to the conclusion that the injectors are gummed up (the engine hadn't been started for well over a year) and not opening. Multimeter showed ~14% duty cycle on the injectors, but no fuel going in. We've pulled the fuel rails and will get them cleaned and see how we go. Weirdly, no fuel is being returned to the tank either - maybe the regulator is blocked as well.