I created a software package that aids electrical engineers with common calculations used on site (substations to be specific). I created the package in my own time, without being asked and without guidance. The package is now widely used within my company and I intend to distribute it nationally.

Do I own the copyright? My contract does state that all work produced is theirs, but this was outside of work and outside of my 'scope of work'. My company is mainly a civil and construction company and had no influence in the creation of the program.

From comments: This is the paragraph "During the course of your service, you will disclose to the company all information, formulae, processes, inventions or improvements which you have learned, discovered or evolved during the course of your service or in connection with the business of the company and will sign any necessary documents to enable the company to obtain patent protection whether still in the company service or not. " They are taking it seriously and have got their lawyers.