Wanted to revisit this post following a number of successes in case they help anyone else...
We did a few things initially, we got totally packed lunches at school except for Fridays when chips are always served as part of school meals. We then backed right off - she eats a consistent breakfast, the same packed lunch every day and I don't worry if she doesn't eat much dinner.
Next, about a month of this later, we booked 'the rainbow fairy' www.iknowwhyitsyummum.com who does fruit and veg parties for her birthday. As well as somehow magically getting her to try a bunch of different things as part of food games, she and her friends have learned loads of songs about veg and why to eat them... weird but it works.
Following that we've had lots of mini breakthroughs - school friends getting her to try baked beans - and her liking them..., her helping cook dinner one night and agreeing to try a bit of it (after I told her she couldn't as it's all mine...) and finally trying a few techniques like sitting her in front of the TV and feeding her myself with a spoon (totally opposite to the normal advise but hey it's not like that was working... the distraction seems to have helped her try stuff without fear!
Also been trying 'food chaining' (google it) which has led from being able to tolerate Apple and mango juice to willingly trying mango chunks and now loving them, and (I know it sounds like ridiculously small progress) going from having only frozen peas to first cold defrosted peas and now warm cooked ones!
All told a few things seem to be working for us finally.
Good luck those others of you who were suffering.