Can I swap a micro sim card on contract for a nano sim card?

I recently took out a 2 year contract with o2 about 6 months ago for a Nokia Lumia 820. I have had nothing but trouble with the phone, and have already spent money repairing it, and it has unfortunately broken again, and for the money it will cost to repair and no doubt for future repairs, I'm going to buy an iPhone 5. My Nokia Lumia 820 uses a micro SIM, and iPhone 5 uses a nano SIM, so I was wondering, if I get in contact with o2 and inform them of my dilemma, will they swap my micro SIM for a nano SIM, but with the same number/contract details etc so I can continue my contract with an iPhone, and if so how much will this cost and how should I go about it?

You should be able to swap your micro-SIM for a nano-SIM at an O2 outlet free of charge - you won't need to change your number, contract, etc.

I'm sorry to hear of the troubles you're having with the Nokia Lumia. I may be able to help you if you explain the issues.

Hope this helps