Company over draft, how much and Credit card

Hello,

Need some advice please, I have my own limited company and for the past year I have been working as a consultant to a small company who are about to close their company and they are allowing me to take over the clients they have and deal directly with them which will mean invoicing directly, their accounts dept. tell me most pay on 30 days and most suppliers get paid on 30 days also however I think I'm going to need an over draft for my limited company, I expect my annual turn over not to exceed £200K with approx. £20K a month going through the company, at present I have about £2K in the company account, I bank with Santander, what would I need to do and how much over draft will I need, also does it make sense for me to have a company credit card? Thanks in advance for any advice, always appreciated.