Excel formation and consulting looks like an interesting niche. It is really business oriented, quite large, with a lot of people probably willing to improve. How did you reached your initial customers ?
This very good start seems to prove it. I wish you good luck.
I have been writing about Excel for last 3 years at my blog - http://chandoo.org/wp/ Once the blog gained momentum, naturally I made it a business by offering few products and training programs.I use my blog as sole marketing platform for finding new customers and convert existing readers to customers (apart from offering kickass content...)
This very good start seems to prove it. I wish you good luck.