My return got lost in the post. After providing proof of postage by email, I received a reply three days later to say the refund would be in my bank account within 3-5 days. 10 days later I'm still waiting. I called today to check on progress and was told they would issue the refund again because the first one hadn't worked (?). When I asked why the first one hadn't worked, I was told that before they issue a refund they have to do some checks, which doesn't really answer the question. I gave up trying to understand. Fingers crossed this time it will work!
If you use Boots Online and need to return something, make sure you are on the ball and actually receive the refund. Overall, it's a pretty stressful shopping experience.