If you start a limited company, it will pay corporation tax on its profits at 20% nine months and one day after the end of the accounting period. Take a look here
for information on running a limited company and here
for information on corporation tax.
If you take a salary, the company's corporation tax liability will be reduced by 20% of the salary but as you already earn a salary in excess of the personal allowance, you will pay tax on it at 20%. If it is above the starting threshold for NIC, there will be employee and employer NIC to pay.
If you take dividends instead of a salary, whilst the company will not get a deduction for them, they are treated as basic rate tax paid (albeit that the notional tax credit is only 10%) and you will have no further personal tax to pay unless your total income exceeds £42,385 in the 2015/16 tax year. Take a look here
for information on dividends and tax.
I hope this helps but let me know if you have any further questions.