Always lovely to have a new cat slave join up! Did this problem coincide with the change in work pattern? Inappropriate toileting or spraying can be a sign of a health issue, it can be stress related or it seems to be just what some cats do. We have quite a few regulars used to dealing with this sort of issue, and I am sure they will give you a more detailed response than I.
First thing to suggest is use a biological washing powder or product specifically designed to remove pet urine if you aren't already, it may be that your work clothing now smells (to a cat) like Stevie and he feels the need to keep topping that scent up.
Secondly you could try a Feliway plug in which many swear by for calming cats.
Thirdly you might look at how well your cat is occupied when you are not home - it may be possible to build a secure run in your garden or catproof the whole outside space so Stevie can scent mark and explore his territory in safety. Also look at whether you can keep him better occupied with food and toys: food-wise you might purchase a feeding ball (e.g. Slimcat), make your own intelligence toy (YouTube 'Katzenfummelbrett') or try some RAW bone-in meat such as a jointed chicken wing.
Toys you might look at for solo play include the Bergan Turbo Track - which my indoor boy
- or something as small as a mylar ball (like a foil Xmas tree decoration). There are loads of cool cat toys on the Purrsinourhearts shop including the TT. Do rotate which toys you leave out as cats are intelligent and therefore easily bored.
http://www.youtube.com/watch?v=iIgdVucDeVUFourthly you might look at changing your routine when you arrive home to break this habit. Some pets suffer with separation anxiety and in those cases it is advised to not make a fuss as you leave or arrive home. Not saying Stevie has separation anxiety as I am not a veterinarian or behaviourist, just that this technique might be worth a try. I wouldn't think of bringing another cat into the home until you are confident Stevie is settled.
