Your company will pay corporation tax on any trading profit it makes. As a director, you should register for self-assessment and complete an annual tax return. Whether you will have any tax to pay personally or not will depend on the level of income you take from the company and whether it is in the form of salary or dividends or both.
Take a look here for information on dividends. The first £5,000 of dividends not covered by your personal allowance will be taxed at 0%. Assuming your total income is no more than £43,000 in 2016/17, you will pay tax at 7.5% on the balance of your dividends. In your income exceeds £43,000, the dividends above that level will be taxed at 32.5%. Use the calculator here to play with some figures.
You will NIC if your salary exceeds £8,060 per annum. Look here for the NIC thresholds.
If your company made £600K in profit in a year, it would pay corporation tax of £120,000.
If you had a company car which was available for private use, the company could claim capital allowancess which would reduce its tax liability but you would pay tax on the car benefit. Look here and here for more information.
Look here for the types of business expenses you can claim.
You should detailed records. Don't dispose of any receipt, no matter how small.
Look here for information on using your home as your office.