How long does it take a credit card transaction to process?
as soon as you make your purchase, it goes through immediately.
Can a business with a merchant account issue cash advances or is it just the banks?
You need a special merchant account to do cash advances...there is a little bit more underwriting, to make sure you're not laundering money. However instead of being charged fees you actually receive some from their bank and if you want you can charge a fee on top of that.
What is difference between related company and fellow subsidiary?
A related company is a company who has similar or the same management or key personnel i.e. they share the same directors etc.
A fellow subsidiary is a company who shares the same Shareholders as another company i.e Holding Company A owns 100% shares in company A and company B. Company A & B are then Fellow Subsidiaries.
What is the fee charged by retailers for accepting credit cards?
Retailers will rarely charge a fee for accepting payment from you the customer, they accept fees charged by credit card networks and processors, called a discount rate. The fees are based on Interchange categories that vary by card type, with debit cards being the least costly and rewards and business cards being among the highest.
You will need to become incorporated in the UK. Once you've done that you can get set up with a merchant account (with HSBC or another bank/ISO) and begin processing once the connections are complete to your gateway/shopping cart.