I'll reply in more depth later as I am fighting the daylight to feed the animals we keep, but to save anyone wasting their time, I unticked both used fixed IP address and reuse last IP address, and whether by coincidence it then found the RP

At least I haven't broken it.
I am now struggling (I know, I am hopeless with this..... sorry), to get audio from HPSDR to WSJT-X
I normally use stereo mix on the motherboard sound card, with all Windows sounds and sound notifications turned off and it's worked fine with HDSDR for years. I am not sure if something this simple will work with HPSDR though? I loaded a single VAC cable and that just seems to transmit a slowly oscillating noise, which shows as a slowly rolling wave on the waterfall of WSPR in WSJT-X
I also failed miserably with getting HDSDR to work with the single receiver software, but I don't know how to tell if HDSDR is "seeing" the RP. I have the right .dll file in the root directory of HDSDR. I also loaded the *TXX.dll file in the old version of SDR# that's supposed to accept the plug in and that didn't work either.... What a dunce I am
Thanks for your time Pavel, it's much appreciated. i will persevere later!