You know the sort of stuff - camisoles, white T shirts, thin jumpers for layering under blazers etc....
I'll start. I had been looking for a white boat neck top with 3/4 sleeves and was surprised to find one in M&S the other day for the princely sum of £6.50 
It isn't perfect but for the price I was impressed! It comes in other colours too: www.marksandspencer.com/no-peep-striped-corset-shirt/p/p22240201?gclid=CjwKCAjwgabeBRBuEiwACD4R5uQE4_zGrRDO7VbsKI1A93IMU3fFTX2uDbRQZ3yFKKYJv2luMVdH1BoCkfMQAvD_BwE&pdpredirect
I know a lot of people rate Uniqlo for basics but I don't really like the fabric of the one white basic top I've got from them. Seems too hot and thick!
Where do you buy your basics?