Well if you're thinking kittens or younguns then two is definitely a better solution than one as kittens needs lots of attention and variety to keep them entertained. A play mate is ideal. Once you've sussed out your costs like food, preventative healthcare - the vets visit you usually have to pay for and vaccinations etc, insurance for unexpected illnesses, safety, indoor/outdoor, then you can make an informed decision.
Also if you prefer only one, maybe consider an older cat that wants to be an only cat?
There are some rescues around in your area, may be worth getting in touch with one of them to find out more and maybe get your prep work done.
http://www.coventrycatgroup.org.uk/ is a great place to start, and Angie one of our moderators on the forumis a fosterer for them.
Good luck !!