travelling to UK with iPhone 6 - what do I need to charge phone?

You just need a USB charger that has a 3 pin UK plug. Your existing USB to lightning/ 30 pin dock will work from the charger to the device.

If your charger has 240V AC as an input it will only need a converter that changes the socket connection.

Bear in mind some chargers output less current, so the device takes longer to charge, this seems to cover it…

Everything you wanted to know about charging your iPhone or iPad

Use everything as you have it already. Buy a standard plug-adapter fot the mains plug, and you can use that for all appliances.