Well they stopped replying to my emails about it. So I posted on Facebook about it, attaching a screenshot of the tracking that hasn't updated since Wednesday afternoon.
They've now sent me a message on Facebook apologising, and offering to refund the shipping charges. The strings are coming from Germany, despite the website saying that they're in stock at shops over here.
It's very annoying, I was hoping they'd be here for a gig I have on Sunday.
I paid £54 for them, they're £79 at Strings direct, but I think Strings direct have better customer service.