Although the smell seemed to be urine based, it was worse in the area of the house where the kitchen and bathroom are.  I was thinking it was just be the old carpets in which case i wanted to rip them up and polish the boards.  I am now worried that there may be urine in the boards themselves, or even worse – a serious problem with the plumbing
I did not ask the REA as i wouldn't trust his answer.
I will have another look this weekend.

Thanks for your advice guys, more advice is always welcome!!