Nikon Silver Efex Pro2 ?
Let's see if I can help here.
1. Silver Efex Pro 2 isn't a Nikon product. It's made by Nik Software, a separate company.
2. It can be used as a stand-alone product. You have to save your image - preferably as TIFF - then go to SEP2. Details can be found here:
Note that this procedure requires the LightRoom version of the Nik products.
3. Nik products are no longer distributed except by download. I don't know if they have a UK Web site to do so. I suggest you contact Nik Software U.S. to find out how to purchase the software where you live.
4. Nik has been bought by Google. Many times when a smaller software company has been taken over by a larger one, the products of the smaller company have been discontinued, absorbed into other products, ceased to be updated, or metamorphosed into something different. So be aware of these possibilities if you go with SEP2.