Cats are ECTREMELY sensitive to any form of change. Elimination problems are the most common reason pets, mostly cats, end up being euthanized or given up.
It sounds behavioral. More than likely this is his way of telling you he is not happy about the change. He may get used to it, and the problem may resolve.
It could also be a mixture of behavioral and medical.
Confine wilbur to a small area for a specific period of time(from a week to upwards of a month or more etc). Usually a bathroom is the best place. If you can, get a urine sample, and have it tested at your vet. This will rule out a medical problem. Once you know it is behavioral, we can go from there on solutions.