Perhaps there some upgrades that BT are doing thats affecting the 2860. I have your model also, with same issues.

Thanks for the response - I've got a call tonight to see if they will tell me.

I myself had several issues like this with the last few firmware upgrades. Got so bad 1 month ago with the latest firmware, I ended up switching back to the HomeHub 5 until my DSL recovered. It had got that bad I couldn't watch the UHD BT Sports channel as my connection dropped from 76mb to 18mb.
Now it's recovered, I've now gone back to my 2860n with the standard Firmware without Vector support and a clean install. Currently its been up without disconnection now for 3 days. The BT hub does not like more than a couple of wireless connections, especially if your using the UHD Sports channel, if the connections start to drop again I'll have no other option but to revert back.

Thanks - I've raised another ticket.
It seems Draytek are not validating firmware releases.

I'm looking though the post and it seems some people are having luck with 3.8.2.2_STD. Where is this? I can see 3.8.2.2_non vector, is this it?
Sorry for my ignorance.
If it isn't, does anyone have a link?
Thanks

The STD is the non vector version from the downloads page. I hope it helps you, so far I have 365 hours of PPP uptime with that version.