UKH

What size pack are people genrally choosing for a light weightish,3 season overnighter?

My do everything is a 47 litre from Aiguille Alpine made in Staveley in the Lakes

About 40 is doable.  

Including climbing gear or not? 

35-40l should be plenty if you are doing it lightweight. It all depends on your sleeping set-up really as that's where it takes up much space for an overnighter. I am also a fan of attachable rucksack pockets (like this: https://www.aiguillealpine.co.uk/product/rucksacks-bags/a035/ ) that you can use for a walk-in to a bothy or a basecamp. That way you ditch them as soon as you reach your base and then pack them flat as there's less food to carry back. 

I have done 9 days (with all the food!) in a 40L pack, but I was lucky I got away with that. Apparently, a paperback book is not a substitute to a sleeping mat in Scotland. The very next summer I tried a 19 day Munro-bagging adventure with the same 40l rucksack, but I gave up 3 days after due to the weather. 

40L for me for somehsome like that.

I’ve done it with a 35l pack for one nighters and ended up with half the tent strapped to the outside - not ideal. But my sleeping bag takes up a lot of room.

just gone for a 45-55 extendable Lowe pack and I think it’ll be a lot more practical and comfortable. I might even take a bit more stuff, on the test walk, fully loaded, it was more comfortable than the smaller pack.

I’ve got two or three nighters in mind. Nice to have flexibility.

Their stuff is really good. I had one of their early packs and it lasted forever.