I stated at the beginning of the process that this was going to be a Forge World project, I have however made a small concession in the form of the Honour Guard.
It is a pack that I've had my eye on for some time, though at £37 it was an unnecessary purchase as it did not fit in with my Blood Angels or Space Wolves. Now however I have an excuse.
There is a reference to Honour Guard in Know No Fear, admittedly they've been gunned down as they board a transport ship, but the point is that they were there and from what I have read there is a place for them in the Betrayal codex.
I was concerned that they would look out of place with their armour being of a later variant. However, with all of the embellishments there isn't much armour plate on display and the helmets are custom anyway so in all it was an unfounded concern. I am stuck on the backpacks though as these are Mk VII (I think) and will look out of place. I've emailed the good people at Forge World to see if I can buy some extra Mk II backpacks as an aside to the order I'm putting in at the end of the month. Hopefully they will be able to work something out as I'm going to be spending quite a bit...
Sadly I won't be using Marneus in the Heresy army as his Terminator armour is of a later variant so he will be a stand alone piece, this is a bit of a shame because it is a fantastic model, but you can't have everything.