I have used Groupon for many years for personal deals & gifts, both in the UK and in Spain but my last experience has left me very reluctant to use again.
Purchased a deal for my mum for Christmas of three beauty treatments in a salon in Worsley, Lancashire. When she tried to book, they would only allow express treatments (not stated on the advert) and were extremely inflexible, even when my mum offered to only redeem for the two that she wanted. They also asked for the voucher upfront so they could claim the payment.
When I approached Groupon, they simply offered a refund in credits to spend on another offer. Poor customer service, no interest in retaining busines and no offer of compensation or apology. Will not be using again after this and would urge others to use Wowcher, LivingSocial or another competitor.