DF and I went to view a wedding venue and we loved it and very nearly put the deposit down on it. When we got home,someone mentioned that it was on Groupon for the same deal, the only things it didn't include where little things like chair covers and a centrepiece which is included in their normal package. All of the food on the menu is the same, you get one less drink with the wedding breakfast but I'm sure people would cope.
Overall though the saving would be over £2000.
They obviously didn't mention the fact that their venue was on Groupon when we were there but it's such a huge amount of money to save.
It's even cheaper to add on day guests in the voucher (works out at about £62 pp rather than £75)!