D,
I phoned my Vet on this one, and he said the stress of moving house can cause this, and often does..... I also found a similar answer on a webpage which I've posted below
What Can I do if My Cat is not using its Litter Tray?
Firstly it would be best not to punish him/her (as tempting as this can be) as it only increases anxiety and does nothing to correct the behaviour. There are various things you could try. Firstly, more litter trays, ensuring they are spotlessly clean, placing newspaper under the tray to catch any spillage. If you have recently changed your cat litter it may be best to go back to the original brand of litter. Confining them to a small space where they have only the choice to go in a tray or their own bed. Any other space could be used up with food dishes. This could help to re-establish correct litter training. Try cleaning the area with some biological detergent followed by a spray of surgical spirit. This should help to get rid of the scent.
Stress can also cause this behaviour, for example, a neighbor’s cat, a new cat in the household, a new baby or moving house. You could try feliway, a plug-in diffuser, which is used to reduce stress and can be purchased from the vet. Finally, in the case of incontinence or a urinary infection contact your vet for advice.
I hope this helps Chester!
