I always order my PCBs from JLCPCB, and I’m very happy with them. They’re extremely cheap for small quantities ($2 for 5 small PCBs). Turn-around time is only around a week, perhaps 2 weeks now with the virus. However, shipping costs can be a fair chunk of the cost if you opt for fast delivery. Ordering from the website is super easy, just upload your Gerber + drill files in a zip.
It’s also very easy to combine orders with others to save on shipping. Unfortunately I don’t need any PCBs right now. Perhaps @Calum_Nicoll or @Gawain need some PCBs made?
Happy to help if you have more questions!
The wemos d1 mini is a great chip btw, I’ve been using it a lot as well (and now their D32).