Hi Patrick
Apologies for the delay in responding, I have been on holiday 
Thanks for the tips! Useful to know the RAID group / vDisk arrangement in terms of controller ownership.
You were right about the costs.
SFF / 2.5" is definately our preferred option, we have narrowed it down to one of 2 disk arrays (EMC came in at a really good price which was a surprise!):
EMC VNXe3150 2.5" dual controllers with 12 x 600GB 15k 6GB SAS drives)
or
HP P2000 G3 MSA FC/iSCSI DC SFF Array (12 x 900GB SAS 10k 2.5" DP ENT)
The P2000 G3 Is slightly more expensive I believe, but its just coming down to performance now (there probably is not a lot in that since we are going with 1GbE iSCSI anyway, apart from the obvious spindle speeds) and scalability / future proofing (the FC port on the P2000 is a big winner here).
Do you have any experience with the VNXe device?
Thanks for all your input