This led me to use an online images editor (pixlr.com/editor) which seemed great for simple mock-ups. Plus it's free and you don't have to download anything so it's good if you don't have a lot of disc space.
I then played about with the levels and such, I think one of the next three options is close to what I'll do for the final work.
I'd love to have the resources right now to make a lino print version of this, I think the bold lines could work really well.
Also, check out www.facebook.com/stillsoldout if you need a laugh.