So I successfully downloaded the update and happy with how it went. I got the EU map update which includes UK and all european countries.
I did a usb update for the 2012 GS450h (found out this is generation 7 for sat nav purposes). I have to say the support was excellent and you can easily contact the seller- I contacted the seller via whatsapp (number on his website) with questions before purchase and during the installation process and he answered pretty much straight away.
In summary all you need is a pc with at least 40gb hard drive storage remaining, a usb stick (I ended up purchasing a 64gb due to size of download files being slightly larger than 32gb), a decent internet connection, and a bit of time. When I connected the usb to the car it took 93 minutes so I just left it on the car drive behind wife's car and stayed indoors!
I also downloaded it all and extracted the files using Mac (although Windows is slightly easier). If using Mac there is a small program (free) you need to download to prevent the Mac installing extra files onto the usb. Ask the seller on whatsapp if you need help with this, he provided me with a step to step guide over whatsapp.
I'm not exactly the best with technology but I did get there in the end and it all works fine. Hopefully the update from 2012 to 2017 maps will make a difference.
Overall highly recommend and much cheaper than dealerships I'm sure.