London in January is the best-kept secret for theater fans and museum buffs. The crowds are thin, the hotel rates drop significantly, and you can actually get a seat at those popular West End shows without fighting off a million tourists.
A trip like this usually runs about $4200 once you account for flights, nice hotels, and tickets. If you want to spread that cost out, you can use the Citi Simplicity® Credit Card, which offers 0% for 18 months on purchases and balance transfers from date of account opening.
Remember that the 0% period is a deadline, not a gift. If you still have a balance on the card once the 18 months are up, the bank will start charging interest on whatever is left over.