@Burr, aye the single sided loft works fine but its the shell not the loft that is the issue in this case.

@Michael, yeah I see there the problem and initially wanted to use network for this shape but that wouldn't work with just the three splines the way they were arranged. So I did split the lines (like manz suggested, (thanks)) and used a blend to create extra lines so network would work and that makes for nearly perfect results - just some funny nicks at some junctions which can be sorted out in post if needs be.

Cheers