As @artful_lounger has said, it would be quite difficult for you to still obtain funding to be able to do a second (BSc) degree. From my experience at Lancaster University at least, it is quite easy to change between these degrees as they are very similar. Our first year Lancaster Environment Centre (LEC) BSc courses - including Ecology & Conservation and Environmental Science - all share a very similar, if not identical, first year which makes changing between them very easy, and you get a taste for a wide range of sub-disciplines within this area of study. After first year, very few modules are compulsory, and you can tailor your degree to exactly what you want and any particular niche you find interesting.
If you have any questions about the department, don't hesitate to get in contact!