I managed to get a good deal on Amazon, just before they sold out again! The link will take you to Amazon, but be careful where you're buying from and take note of the seller: I bought directly from Amazon and got a proper UK D500; other sellers - particularly if the price is low - are offering grey imports but not labelling them as such. Just be aware.
At the time of writing this, there is one available on Amazon - not sold BY Amazon, however - for under £900. Very, very, VERY cheap! I would be extremely suspicious of this seller...
As they say: if it seems too good to be true, it probably is!
I've taken the D500 on a couple of shoots so far, and whilst I haven't pushed it to it's limits yet, I am pleased with the results.
Not my best images, but here are a couple of quick edits from my first outing with the D500:
These were taken at various ISOs and shutter speeds. It was very windy that night so not the best conditions but a good test. Now I've really got to grips with the D500 a bit more I'm starting to see even better results. Some of it's features - such as Wi-fi connectivity for remote shooting through your phone - are going to come in handy; I might put together a quick video at some point.
But for now, it looks as though the Nikon D500 is going to work as great for astro landscape photography!