I often use an interest free credit card for large purchases, cars, furniture, other house related stuff, eBay etc. You also get a bit more protection from the card issuer on a credit card purchase.

Once my 0% deal is about to expire, if I have any remaining balance I will simply apply for a new 0% balalnc transfer and purchases card and transfer the balance (usually there is a 2% charge to do this so I try and avoid it).

My last car i bought was 10k, it all went on a 0% credit card, I paid 4k off straight away with the sale of my old car, then paid off a grand a month so the debt was cleared in 6 months, without paying a penny of interest. Of course you have to resist the temptation to blow the lot on shit you don't need.

My dad also uses a credit card for every purchase he makes, as the card issuer gives him points that he can use for cheaper holidays etc. He clears the balance in full at the end of every month so never pays any interest.