WARNING - Long rant ahead, but want to share so that anyone returning something to Groupon is aware.
Ordered a necklace & earring set which were meant to look like hearts but when they arrived the links were in the wrong place and so the pendents looked like the letter 'B'.
Contacted them to arrange a return and was told I need to print out a label. When I told them I didn't have a printer I was basically told I couldn't return it. It wasn't until I threatened to not use them again they changed their minds and said they would give me the address to send it to but I would need to pay the postage. So sent it back with my return ref on the front and highlighted the return address they had stated, and got proof of postage, which I emailed them a copy of.
After a few emails being exchanged as to the status of my refund I was asked for my proof of postage with a tracking number on, which I wasnt told I needed to obtain, just told to state my return ref on the label. Now they have turned around and said that they have no record of it arriving there and they won't refund me. What a coinsidence!!
Emailed them saying I was not happy about the whole thing and wanted the matter taking further, and what a surprise I had no response.
Have had some advice from Citizens Advice Bureau, and have emailed Groupon again. Yet, still no reply.
FUMING!! 
So if you are wanting to return something to Groupon I hope you have a printer, or are prepared to pay a daft price for a tracking number. Otherwise you may experience similar to the above.
Thank you for reading.