Martin,
I direct you to the three pages that outline the level of treatment that will likely be required in this situation.
http://www.another forum.co.uk/?board=carp_clng;action=display;num=1088375127
Some of the products mentioned will be hard to source, so alternatives will be required.
Whilst reading, consider that you will likely have to remove the furniture from site, unless they can provide a suitable venue. A warm location would speed the process.
As an alternative approach the articles could be saturated in urine neutraliser , then encapsulated in plastic sheeting for 24 hours, then extracted/rinsed/extracted/rinsed until properly flushed.
Although shutting the items in a sealed room with a powerful ozone generator would remove the odour, since the uric salts will be present deep within the foam, the effect of this method is likely to be temporary.
Other considerations is to decide how well the face fabric of the carcase will stand up to prolonged soaking and whether any urethane on the padding has been seriously affected.
This is the sort of job that can drag out in both time and cost.