you can either get an all-in-one payment gateway and merchant account such as 2checkout.com, authorize.net or worldpay.com or get your client to get their own merchant account with their preferred bank and get a payment gateway to process the card and deposit the funds into their own merchant account.
We recommend using Secure Trading to process the payment.
Secure Trading costs are £195 per year plus 1%-1.5% of transaction value.
In the UK, merchant accounts typically cost £200-£300 to set-up (no annual fees) plus 2% on credit cards and 20-30 pence on debit cards and they hold onto your money for a period of time (24hrs - 10 days). They may also impose other restrictions based on your trading history.
Single supplier (payment gateway plus merchant account) costs vary in terms of set-up fees, annual fees, transaction fees and payment delays.
If your turnover increases you should always ask for a rate review too.