Thanks for the response.
The IP is assigned via DHCP, but it is reserved so wouldn't change... but in any case I thought Wake on LAN used MAC addresses for sending the magic packets (at least in the Solar Winds app I'm using).
The NIC Link light actually goes off after Windows 10 is shutdown - I've spent hours trying to find the setting to stop this happening - however this isn't necessarily the only issue because if I turn power off at the PSU, then back on again the link light does come on, but Wake on LAN still won't work!
I don't think it's the switch, because I have 6 other PCs connected to the same switch and they all work fine with WoL.