Tax deductable items:
PC for work use
Phone for work or private
Any genuine tools you need for the job etc
Use as home as an office
Travelling (about 40p a mile tax free if you use your own car)

Any of those items you wont pay any tax on at all

Other things to note are that you can have your wife as a director perfectly legally, she doesnt have to do any work for the company at all and can be paid money in dividend form which will be taxed a whatever rate she is on (23? or whatever) and will attract NO national insurance contributions.
(providing your arent an IT contractor or similar caught by IR35, which is what dunccoss is getting confused with i suspect?)