I had a big party for my 40th, and I had a budget similar to yours. We had 150 guests.
For food, after much thought, I did a baked potato bar. I used slow cookers to make veg and meat chili, platters of grated cheese and some pulled pork/salad. All the potatoes were baked, pre wrapped and frozen, then re-heated on the day. Look on Pinterest for ideas.
Friends made cakes for desserts, plus my mum made me a big cake to blow out candles. (For my best friends wedding last month, I also made her cake. I loved that I could do that for her. Look up nude cakes, simple and trendy!)
We used the village hall, and I put our welcome drinks, but then asked everyone to bring drinks in lieu of presents.
The biggest expense was the live band (I had a ceilidh) but then after that, we just had an iPod plugged into speakers and everyone took turns in choosing songs.
For the bar, I was planning on working it, and being able to chat to everyone but friends threw me out and did it themselves. There were lots of outrageous cocktails being made!
For decorations, we saved tins and had tealights, pansies in tins, and also threw a few pine cones and conkers on the tables. My sister made me masses of some very simple bunting, which really added to the spirit! I loved it!
It was brilliant and went on until 5am.
The whole thing cost £2k, plus it took us 6 months to drink all of the excess alcohol!
Friends with phones are often the best photographers. You will be amazed how the photos will come out.
It can be done, if you are willing to put the graft and planning in, and it's amazing how many people are willing to help!
Good luck.