Replace copper pipes?

Personally I would suggest getting a section of the pipe which is damaged and causing the problem replaced in order to keep the cost down and to also protect the new pipe with a thicker sized pipe over the top to work as an insulation and protect the new pipe.
Obviously if your already having new flooring laid and can afford it then by all means having everything laid new can sometimes give you piece of mind but I always say if it’s not broke, don’t fix it.

It’s a good idea to consider replacing the copper pipes, especially since the pipes are 20 years old and have already caused significant damage. Over time, copper pipes can corrode or develop pinhole leaks, particularly if the water has high acidity. Replacing the pipes now could prevent future leaks and save on potential repair costs. While it may involve extra expense and inconvenience, it could be a long-term solution to avoid similar problems later. Consulting a private plumber to assess the condition of the rest of the piping would be a prudent next step.