Hey mate,
Long story short, i was able to load it into Illustrator (layers and guides didn't show, just all the curves in one hideous list), then it needed to be exported as an Adobe PDF to be read properly with the layers and guides. I just signed up for Illustrator for a month, otherwise i don't need it. However if this comes up again which it likely will i'll still need it...can't get away from it!
I tried all the PDF export settings out of Affinity. Also, when applying any masks in Affinity, they didn't render out as vector so when loading in Adobe, anything with a mask or effect loaded as a terrible jpeg like image, not sure what settings or process avoids this?
Could you tell me the settings you exported with out of interest?