I put a similar deposit down in March, but then cancelled at the beginning of June. They didn't want to give me my deposit back initially, but then I pointed out that I still hadn't been given a build date - and I could have just waited until the car (with it's £10k worth of options) had been delivered to them and then cancelled. In the end they relented and paid my deposit back in full.
Having said that - I am now regretting the decision to cancel and am looking to re-instate my order next week. Maybe if you are serious about cancelling, I could take over your build slot if the spec is still changeable!
I was told my 2k deposit was none refundable. This might be because I originally put a 1k deposit down in January 2015 then, mistakenly in retrospect, cancelled in June 2015, so perhaps second time round they are more cautious.