if you want to pick your own name for the ltd. co., then contact companies house ( google it). you pick the name you want, they tell you if you can have it, you fill in some forms and pay a small fee. don't forget, you will have to submit annual accounts to them.
I've done this recently, I used a company online called blue sky formations. I paid for the top package about £120, but wish I just went with the package that has a printed certificate, as so far when opening bank accounts e.t.c that is all they have asked for. I can thoroughly recommend barclays business for the banking as well. If you use them you get an online accounting program called freeagent which makes doing the books, and invoicing and estimating a doddle.
Just one little bit of advice, if you are setting up as a limited company so that you are protecting yourself if the worse come to the worse and you went bust for a large mount of money, when you set up your company close down all your wholesalers and re-open them in the limited company, as i know someone who didn't do this and when he went bust he was still personally liable for the 30k to the wholesalers ,as this was set up in his name and not the limited company,,
There is a fine line on the decision. Why do you want to go ltd?
When i set my company up i weighed up the options for ages until my accountant basicaly told me to go Ltd. Luckily for me he is a good friend too and explained all the pro's and cons.
The main decision for me was because i have a military pension coming in and i needed to be able to limit the amount of money coming into the house because of my partners income and various other things. You have to be careful though, for example, profits made by the business will be subject to corporation tax, if you then pay yourself out of those profits, they will be taxed again. What you need to be able to do is ensure that at the end of the tax year, you have paid yourself what you want from the business and that the profit for the business is zero or less !!
It's a complicated system, you need to have an accountant (who will probably pay for him/herself through thier advice).
As Eddie says, the 'Ltd' part of the deal limits the amount of liability of the company with respect to damages or loss to clients. Being the Director of the company, you are still liable for debts etc incurred to the company. ie you will not lose your house if you f*&k up, but you will if you are responsible for accumalating debt on behalf of the company.
I hope this has helped a little, it's a big decision to make buddy, good luck.