My friend bought anphone that was locked in London. After a few weeks Apple sent her the code to unlock it, this has worked but now she can not use the local networks in Cyprus. What can she do? They say it needs unlocking for Europe and it will cost

Apple doesn't send any "codes" to unlock iPhones. The only way to unlock an iPhone is to use the cell providers process that has the lock on the iPhone so your friend will need to contact that provider and follow their instructions.

Who is "they"?

Apple would not send your friend any kind of code to unlock the phone - Apple does NOT get involved in unlocking of phones.

If you purchased the phone from Carephonewarehouse, then the phone will be sold as sim free which means that it will lock to the first carrier sim card that you put into the phone and you will need to contact the carrier to have the phone unlocked.

Carephonewarehouse cannot unlock your phone for you - if the say they can, then all they will do is hack it to unlock it and your phone will then revert to being locked when you next update it.

Contact the carrier to get the phone unlocked - that is the only thing that you can do. Either that or go and buy a new phone that you can use out in Cyprus.

Perhaps you have learned a lesson here - don't buy from Carephonewarehouse again if you want an unlocked phone that you can use - buy directly from Apple.