You've come to the right place. When it comes to cheap and cheerful weddings I'm your gal.
Venue. Try Sundays. You can often get things much cheaper then. Or Fridays are often discounted.
Get as many of your family involved as possible, ask for a contribution in lieu of wedding gifts. I catered my sister's wedding as a present as I was unemployed at the time. We asked my sister in law (a photographer) and a friend who is a part time photographer to take the photos for our wedding. I drove the wedding car for one of my sister's wedding and my brothers have been barmen at others. If you know someone artistic, get them to do the flowers. We asked the friend of a friend to do the disco and made up our own CDs for the first part of the wedding reception.
We got our cake from Marks and Spencer. They do about 4 different sizes, you can also get the pillars from them. I decorated ours with red and white carnations just scattered over it, you couldn't tell the difference from an expensive one.
I made our invitations on my home computer using Microsoft Publisher. I sacnned a photo of dh and in, and used it for the cover. I then printed them off on some nice paper that was 3 for the cost of 2 at W H Smiths.
I bought my dress in the Ghost sale, and dh got his suit in the Paul Smith sale.
We did the whole thing at a posh venue for under £3k. That included a bar bill of nearly £1k, £300 for getting the registrar out to the venue on a Sunday, food, clothes, cake, music and entertainment.