Netgear Nighthawk M2 firmware

My M2 is still running Firmware version: NTGX24_10.13.09.00 and is functioning erratically often having to reset & restart it numerous times before connecting properly. I purchased it through EE in the UK and it has performed flawlessly until recently. EE customer services put me in contact with Netgear technical who were to put it bluntly, useless, saying the router is no good & basically bin it.

Clearly the router is fine and just needs the latest firmware/software. As other owners have reported when trying to update the software the wheel keeps spinning with no result. I have tried updating through the router itself & via the Dashboard settings. 

For an expensive piece of hardware the support is majorly lacking.

Anybody know how to get the firmaware updated? Thanks