Having been used to Hopes with 185mm discs, are the Avid's on the Boardman's at 160mm up to the job, or is it worth from the off upgrading to a 185 up front?

And what is the difference between the G2 and G3 discs?

cheers

The elixir ones?

They seemed suitable. Felt about as powerful as my SLX but a bit more grabby at the start of the lever pull (guess this is the servowave on the slx?).

They are good enough that I wouldn't bother changing them

Can't comment if they're Elixir, but my mate recently bought a Scott Spark with Juicy 3.5's and quite quickly put his old Hope Tech X2s on instead. Big difference, especially in the Lakes when there was a LOT of water about. He was pretty disappointed with them, having been used to the Hopes.

Really robinbetts? My mate took his 3 year old hardtail to the Alps with Juicy 3s (160mm rotors) had no problems. They actually performed better than my XTRs as they didn't overheat (mine did). He's 6'2" and not light btw.

Friend of mine with Hopes is always impressed by how much better my Juicy Sevens feel.
I've got 185/160s on mine, but only as that's what the offer I got came with. 160 on the front would probably be enough for me most of the time.

I'd keep them as they are and see how you get on before deciding whether to stick a 185 on the front.
Not sure about the difference between G2 & G3 discs – probably just a different pattern to aid self-cleaning/cooling or something.