Cheers guys.
My ebay one turned up and once I repositioned the GPS antenna to the window sill it locked in pretty quickly.
I’ve got a couple of NDK oscillators as samples (DOXCO/OXCO) so I’ll make up a board to run them and then see how it looks compared to a 3ppb OCXO.
I’ll keep an eye on ebay for a rubidium standard as well.