Hi, I've performed on the street only a few times but cant seem to get over my performance anxiety, are there any good techniques to getting over this.

Yes, get out and do it. Anxiety is normal just work anyway. When the hats are low we all get anxious.

Yep, MORE performances!

Quoting Nike, "Just Do It" I had the same problem and I can say live performance really helps. In the beginning, before you gain natural confidence, I used to do something I found worked even though it will undoubtedly sound stupid. Pretend you aren't anxious. I found it helped me, at least, to try to mentally convince yourself that you weren't nervous. Make sure you have all of your material down and go for it! Good luck!

A ritual might help. I like to play this:
http://www.youtube.com/watch?v=hO2wA0Te0wM

Having your material down pat will greatly help. It is one less thing to thing about and worry about.

Also, don't worry about screwing up. It will happen. Eventually, something will go wrong. Just accept it, learn from it, and go on. I remember a few years ago, when I was performing the toss out deck, the rubber band came off the deck and cards exploded everywhere. It sucked. But it wasn't the end of the world. Now, I use three rubber bands on my deck, and it has never happened again. However, I know that there will be other problems in the future.

Then as Paddy first said, just do it. Get as many performances under your belt as you can while maintaining a professional show. The more you do it, the more comfortable you will get. It may not make all of your anxiety go away, but it will greatly help.