How much does it cost to repair a broken power button (iPhone 4)?

My iphone power button is completely stuck and doesn't work at all now, i'm under no warranty so how much would it be (£) to get it repaired?

Most is £30, although it depends where in Britain you are, i've seen scotland shops charge upwards of £30 and down south the same, midlands and manchester its about £30

Depending on the problem with the button (Just sticky or none responsive) it can vary from £15 to £30 including labour