I often use some of the vape deal sites to find the best deals on liquid. But generally I purchase my liquid from www.vapesuperstore.co.uk they've got a really good rewards program. Their prices are pretty competitive but if you join the rewards program you earn points which you can redeem on any order later on
I've been buying Smith's Sauce from eBay lately. They do 100ml shortfills and it's buy 2 get 2 free. Really tasty flavours with loads to choose from. From 3 orders I haven't had a single flavour I haven't liked. I used to be into "premium" brands but wouldn't go back now.