We had a very cheap wedding (years and years ago..). A few things we did to save money. We got married in London, so booked a black cab for to the church and to go away in at the end. It cost £30 in total. Today it would probably be about £100 but much, much cheaper than hiring a car and it also means that you have a classic car (the London taxi is a classic) without the cost. Also, loads of space for dress, bouquet etc in the back. Try to get a black one as you don't want to be advertising Easyjet (unless your colour scheme is orange).
We found someone to do the flowers who was "training" and gave him £50 for statement flowers, the rest he liberated (ivy, twigs, branches etc). This was more expensive than it might have been due to me being a Yorkshire lass and having to carry white roses.
Our cakes came from M&S. They do a plain, white iced fruit cake. We had one decorated (with more flowers) by my Mum. The others never saw the light of day, just got cut up in the kitchens and served. Cost at the time - £16 for enough cake for 200.
My sister also had a cheap wedding and she used a bakery but ordered a large chocolate cake and DID NOT SAY IT WAS FOR A WEDDING as this apparently inflates prices enormously. We ended up with a huge cake (sponge and butter icing) which was served with strawberries and cream...Yummy. So it became pudding.
Wine - go to France. Eurotunnel day returns with a car used to be v cheap if you left early in the morning and came back before lunchtime. We did this. We tasted a few bottles of plonk in our local Tesco and then went and bought the same stuff in France.
I will post again if I can remember anything else. The prices are 15 years out of date by the way....