It is impossible to answer the question 'Which is the best credit card currently available?' as it depends on how you intend to use your card.

The trick is to select a card with the characteristics enabling you to save you the most money. This page offers guidance on what criteria you should focus on depending on how you plan to use your card.

Don't forget, as long as you have a decent credit rating, there is no reason why you cannot jump from one card to the next every six months in order to maximise the low interest rates on offer, or even get a couple of cards each with its own advantages. You can then use the card which is going to benefit you most in any given situation.

I will pay off the balance in full each month

You should focus on criteria that does not relate to the card's interest rate. You may want to consider a donation card or a card which offers cash back or reward points. See other considerations for other card features that may be of interest to you.

I always seem to have an outstanding balance on my credit card

You need to focus on the card's interest rates. If you are shrewd you can 'surf' different credit cards, taking advantage of a card's introductory period before moving on to the next card, and so on. Otherwise, you should ensure that the card you opt for has a low standard rate of interest. See interest rate considerations for further details.

I want to purchase a number of items and pay for them over the following 6 months

The introductory interest rate will be of most importance. If you plan on using the card after the 6 month period and do not expect to pay off the full balance each month, the card's standard interest rate will also be of importance. Alternatively, you could always apply for a new card with a competitive standard interest rate at the end of the 6 month period and transfer the balance.

I want to reduce the interest payments on my existing credit cards

You should think about transferring the balances to a new card with a low introductory interest rate for balance transfers. Some cards offer a special rate for balances that are transferred on application of the card which is then held for as long as it takes to pay off that balance. This can be exceptionally useful if it is likely that repayment will take a long time, i.e. at least 6 months.

I want a card to buy most of my essential shopping from Sainsburys and Boots.

Consider getting both a Sainburys and a Boots credit card. Use the Sainsburys card for all Sainsburys shopping and the Boots card for all Boots shopping. The objective is not to build up a debt on these cards but to take advantage of the reward programs these shops offer with their cards. If you shop there anyway, why not accumulate additional reward points that can be exchanged for items in the stores? Do not use ownership of the cards as a excuse to purchase items you cannot afford!