I'd tak the mat, a good night's sleep is worth it imo.
I'll be taking in two Alpkit XT 20l dry bags:
In one: (2.5kg inc dry bag)
Alpkit PD400
Home made micro tarp with ti pegs
MoD Goretex Bivvy Bag
Alpkit Wee Airic
In two: (1.98kg inc dry bag)
Alpkit Gamma head torch
Stuff bag with toiletries and insect repellent
Lightweight fleece shirt
Alpkit Mytimug
White Box Stove
Plastic Spork
Flint & Steel firelighter
Nalgene Hip flask (currently empty)
Lifesystems Pocket first aid kit
Mora Woodcraft Knife
Stuff sack containing:
Ron Hill Tracksters
HH underwear
Two pairs of socks
Spare batteries for head torch and gps
Will be taking my normal Endura Waterproof and cycle spares, haven't included them in the above as I would be carrying them anyway.
Will probably bungee some crocs to the rear dry bag for river crossings and wearing in the pub.
Need to print of the maps, 25 pages at 1:25000, so that's a 1/4lb not included above…