Thanks for the info, I'd not thought to look in DIY stores for something suitable. The guns on order so I don't know the exact length yet, but pretty sure I will want to leave the moderator attached as I believe it's secured by some small grub screws (rather than a conventional screw on type of mod that fits onto a threaded barrel). From what I've read the grub screws are best with a bit of loctite on them and I can't think of any situation when I'd want to shoot it without the being mod fitted.
Ed