I'm getting married in July and on track to spend just under £10k. Few things I've done to save money:
Limit the day to family and very close friends only
Call in as many favours as possible! My step grans cousin is a budding wedding photographer so she's kindly doing the photos for free (plus 2 of our friends are good with a camera), my future sister in laws mum is a great Baker and is doing the cake for cost price only, my H2B is a goldsmith so will be making our rings (although obviously not everyone can be this lucky!). You might be surprised how many people you know can do stuff for you.
Don't have centrepieces. Our venue is beautiful enough without all that rubbish that will only be chucked the next day. I've been to a few weddings and could never tell you what the centrepieces were - they just aren't important!
DIY invites. I downloaded a nice pattern I found from a website call Greetings Island. You can customise them and then save them to get printed. With some clever cropping I got the watermark off it aswell. Cost us £36 in total with printing and got loads of compliments. Again your guests won't care what the invite looks like and they more than likely will end up in the bin.
As others have said - WED2B is your best friend! I got my dress there and it is stunning. Although they do make their money back on the accessories so be careful there. I ended up getting a few accessories for my dress from JJs House instead and it was a fraction of the price.
Don't go crazy with flowers. I'm only having 4 x bouquets for me and the BM's and buttonholes for the gents. No need for anything else.
DONT RENT A SUIT! Go to a website called Suits Direct, some lovely suits there at lower prices than renting. With renting you also have the added risk of losing your deposit or even being charged for the whole designer suit if any spills or accidents happen. Might seem like a better idea at first but will likely end up costing you more in the long run.
The last and probably weirdest sounding one - don't buy bridesmaids dresses. As soon as you stick the word BM in, the price shoots up. I couldn't find a dress to suit my girls and colour theme (yellow and dusty blue) without spending a fortune so I went to JL and got 3 beautiful dresses much less in a lovely emerald green to compliment the colours. Also suits my BM's more - 2 of them are blonde and pale. Each dress was over half the price of the "bridesmaids" dress I had found online and look so much better!
Good luck and enjoy the planning!