Hi bobg. I don't use it, but I do know a lady who owns a D1 who does use it. I have actually seen the car up close running on the stuff and it goes well. If you use it, (it's easy to make) all you will notice is a slight 'fish & chip' smell. It's also supposed due to better lubricating properties to make the engine run quieter.
Thanks for the note.
Being a series II, I am unsure as to whether the injectors can take the stuff. You hear stories either way. One says OK, another says not etc.
The reason I ask is exactly what you mentioned, its easy to make and a lot cheaper!
I can't see any reason not to do it, if the car can handle it.