The best thing to do is try and get a 0% purchase credit card, the longest one seems to be with HSBC who are offering 12-months at 0% for new purchases.
Just use it for your laptop (avoid any cash withdrawals as these won't be included in the 0% deal) and then you can spread the repayments over the next year.
There aren't any fees at all, so as long as you stick to the best way of using the card (see guide above to save my fingers!) and get the balance repaid within the 0% period (up to 12 months) you won't have to pay an extra penny for spreading the cost.
You'll also get the added protection of paying by credit card too! Just make sure the place you buy from doesn't charge a credit card payment fee! Any of the big places like PC World, etc.. won't, but smaller independent places might do - so make sure you ask.
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