Hey ‘redefined’ I recently aquired the neo air xtherm mat too, a mat upgrade for me but haven’t tried it outside yet, crinkles like a crisp bag tho when inflated for inspection indoors, will be interesting to see how it blocks the cold on an overnight trip.
Re bivvy choice..... as well as Rab ascent recommendations, have also had been informed on good authority - from the home office/ basecamp that the ba biv u can’t go wrong with. Initially tho. for the ba biv, just didnt fancy ordering something off eBay with someone’s old foot skin or boot laces in

but I’m impressed with how that one of yrs packs down onto the fork bags there, nice and tidy. Again waterproof breathable and warm are more important than a bit of extra weight.
Meanwhile tested bike set up with fork bags on with weight in at weekend first time and was really impressed how easy it was, not too much impact on steering or general bike handling so bit of extra weight with a biv year should be ok.