Lots of good deals and plenty of sizes available! Can definitely vouch for this Swedish brand and you get free "support" for life, e.g. they can repair purchased (even second-hand) items for you at their shops/repair centres. Also plenty of recycled jeans, which is undeniably better for the environment than buying brand new (even though they would feel like new!)
As per the title you can sign up to become a member for free here: https://www.nudiejeans.com/ (popup about signing up for the newsletter).
Unsure if you'll get access to the pre-sale straight away if you sign up now but hopefully you will within the day! Non-members can access the sale on 17th July.
EDIT: Changed the above sentence to bold as people don't seem to understand that signing up now is not a guarantee that you'll get access to the pre-sale!
Going commando ?