Avon have a good selection of their make-up on a buy 2 Choose 1 Free offer. There's a good variety on offer. Here's 2 of the best codes I could find at the moment (more attached).
For an extra 10% Off & Free Delivery on £15 spend - Use discount code: BESTAPR
Free delivery on a £10 spend - Use discount code: MICHELLE
Only one code can be used per order.