Anyone else come across this before?

I'm trying to do a clean install of MacOS onto a 2017 Intel based Macbook Pro (original OS was High Sierra) and I keep getting this error message at the early stages of the internet recovery process. I've done this dozens of times before (different hardware) and never come across this error before. I've searched and there seem to be plenty of other people with the same issue, some provide "fixes". None of which have worked for me. 

Any help appreciated.