I've placed an order for 10 Off 100mm x 100mm boards, so I'll report back here once they arrive.
The total price to the UK was $23.90 + $6.34 shipping, equating to a total payment of £18.91 Sterling.
I've had some smaller boards via Seeedstudio, which is the same Fusion PCB service, so I'm expecting these back at the same quality, which was very good.