You can extend a steel steerer, but it's quite expensive and the end result will be quite heavy as you have to weld a reinforcing sleeve inside the steerer tube. It would probably be easier to replace the steerer, but the chrome might need to be stripped so that would end up being pretty expensive as well.
Basically you're better off getting a new fork, especially as you can probably pick one up for £20 - 50 on ebay.
You can extend a steel steerer, but it's quite expensive and the end result will be quite heavy as you have to weld a reinforcing sleeve inside the steerer tube. It would probably be easier to replace the steerer, but the chrome might need to be stripped so that would end up being pretty expensive as well.
Basically you're better off getting a new fork, especially as you can probably pick one up for £20 - 50 on ebay.