Latest in Beauty (here) is offering 50% off Bio Effect serum sample for one day only. It’s a small 3ml sample but with this product a little goes a long way. The previous sample I got lasted me for about 2 months. You’ll need to pay ~£2.50 for delivery as well.
I reviewed the serum here and if you live in the UK and haven’t tried this yet, now might be a good time :). Code bio50.