I’ve had similar before. Emailed a few times with quick responses then nothing for a couple of weeks. When it got past the time he said they’d be done and I still hadn’t heard anything I emailed him to see if everything was ok. Didn’t get a response from Neil but I did get an automatic email saying my strings had been dispatched a few hours later.
As it isn’t an especially big company (or workshop, as Trevor said) I think he’s just a busy guy! They have a very good reputation, though, so I don’t think you need to be worried.