I highly recommend you do. I promise I don't work for them although I do know the guys who started it a few years ago.
It's a browser extension you add to your toolbar and then when you're on the checkout page it automatically checks all the available discount codes to see if you can save money so saves you time hunting around for a code.
I've only ever used it for small discounts but recently it found me £200 off our new garden sofa and it's just flagged a £100 code for something I was buying on Aspinal so well worth a download.