Unfortunately, you may find that you get what you pay for. Although there are plenty of average service providers out there who charge more for weddings, the good ones generally know they are good, and charge accordingly for it. Not to say there aren't any cheaper ones out there that are any good, am sure there are but it's finding them and having the faith / peace of mind to go with it.
Set yourself a realistic budget as soon as possible, then if you are at all handy with excel start planning your spending. You can also pop the guest list on another excel sheet, makes it easy to know where everything is. You'll also have to consider whether people can do the exact date you want them to do, and don't forget the church fees / registrar fees.
The biggest expense at our wedding by far was the wedding breakfast, which the wife insisted on for half her family. If you can do away with that, or keep it low key, then you can spend it elsewhere -a car, photographer, the toast, bridesmaid and best man gifts, videographer, flowers, cake, buffet.... it's not cheap unfortunately.
Have you spoken with your fiancee about what she wants? Because, believe me, that's what she'll be angling for 100% and any time you suggest a compromise she will act like you've broken her heart forever.
Oh, and another thing. Not happened to me but I was warned of it by someone with a sore memory - be wary of taking on a friend or a relative or a friend of a friend as a service provider for your wedding. If they aren't in it as their main business they may jump ship on you, and if things go wrong it may sour relations for a very long time.