I already cancelled my wedding once for the same thing and am still going through it. My parents are giving us some money, OHs mum is giving us some money and is also helping us by putting together and decorating the favour boxes for us and OHs dad has paid for our videographer and the fgs outfit and shoes. My parents decided because they are giving us money, they have the right to tell us who we are inviting, what we are eating, what the colour scheme is etc etc.
The money they are giving us doesn't even cover the food at the reception and yet they still thought they should be hosts which is not what we wanted as we are paying for a lot as is ohs mum. (snap to the invitations coming from us and our parents).
My mum and I have always had the opposite taste in everything...colours, flowers, clothes etc which means she hates everything OH and I choose and invariably comes up with another option that either oh and i dont like or that is twice the price of the first one.
When we first started planning the wedding she was terrible, everything we wanted was ridiculous, the ceremony was going to be some major theatrical performance (we are having 2 hymns and 2 readings, she thought 1 hymn was enough and wouldnt accept this is whats required by the church) and although they had offered us money they wanted to tell us what it was to be used for and therefore what we would be having in said category. My mum even picked my bms!!!
Upshot was we cancelled everything, most of our suppliers were really good and said because we had booked 18 months in advance they were happy to hold the deposits to be used against a different date. That was January last year. At the start of July, having put everything on hold we started planning again, this time totally leaving my mum out of it as much as possible. She still has digs about how she doesnt like things and thinks we should have something different but she says she doesnt want us to 'throw our toys out of the pram again'. We have compromised in some areas like the bms and the invitations but are learning to ignore the jibes as well as we can (although some of them still hurt and she will not accept she has ever been in the wrong). We are now getting married a month earlier than originally planned, when we sat down and talked about it we knew we wanted it to be this year. Despite the fact I wanted to go abroad so we wouldnt need any help financially, OH wanted to stay in this country and his family wouldnt have been able to come, with his mum being so supportive we didnt want her to miss out so we are having a very traditional wedding, parents have had SOME say over the guest list but we have put our feet down over some issues (they wanted to invite all extended family children meaning we couldnt invite any friends so that was rapidly vetoed!).
It is horrible when your family can't be supportive but from experience if they arent going to be now, they never will be and although it takes a really huge effort, you need to focus on who the day is about and what the two of you want. You're in a real predicament with the invites already having been sent but I really hope you can manage to invite your friends. Parents can be very stubborn and if they are anything like mine will turn the row so it's your fault. Just try and keep your chin up. Some days it's not going to be easy (can you tell I'm having one of those!!lol) but just focus on the end result and have a 
. We're all here if you need to vent and I promise to try not to rewrite war and peace again 