Well, I got my nexus back, engineers report says no fault found.  Took it home turned it on and it started to go through its set up...... it froze.  So reset it and carried on and when finished it froze.  Decided to video what was happening on my phone and then packed it away and took it back to the retailer.  Showed them what had happened and they agreed that this was not acceptable and offered to replace it.  Unfortunately they did not have a nexus in stock so decided to take no chances and went for a galaxy tab 3.  Sorry chaps but this is like light and dark.  The Galaxy may only be a duel core but my oh my its just great.  So, good luck with your Nexus units and I am sure you will have loads of fun with them, me I have gone over to the dark side     

I decided to take your advice and carried out a full factory reset..........  The stupid thing frooze during the reset 

I have boxed it up and taken it back to where it was bought from.  I have had to settle with the device being sent off for repair as the outlet wont exchange it because it is over 21 days since it was purchased.  The stupid thing is that it was bought on the 1st of Dec and opened on Christmas day, so this 21 day period for return had already expired.  I can only take hope that the shop did say that it was likely, considering the faults, that the manufacturer would probably replace it with a new unit anyway.

I received the device for Christmas and was so excited to get started.  On initial boot up the updated KitKat downloaded and the system was up and running.  Slowly I started to learn how to get going but now, 4 weeks in I am getting rather frustrated.  The device keeps freezing up and I have to stop and start again to get it to work.  When playing video the screen will start to flicker and makes watching a chore.  On a positive note the rest of the device is excellent and I really want to start enjoying it to the full.  Should I box it up and take it back