Is controller + soft synth an option for you? I'm guessing not.
Maybe an Kurzweil k2000/k2500 would suit you, and I think sits in the busdget. There was
this recent thread on Kurzweils. Very well regarded. Not a VA engine in the old ones, though they seem to be very capable and well regarded. Maybe you could get a 2661 for £600; I'm not sure.
I think you would be disappointed by the Lead 1/2 keybed.
I have a Lead 1 rack. I find it's simplicity and immediate hands on interface are its strong points. The sound is clear and bright, and fits well in a mix. It generally won't have unwanted fatness that may take up more room than intended. I also find it reminiscent of analogue subtractive synthesis, although with its own clean Nord character. I have found all Nord filters disappointing in some respects, though. I would have really liked something closer to hearty discrete analogue character. I prefer Waldorf and Creamware/Sonic Core digital filters, and actually most recent VST VAs.