When you have just come up with an exciting business idea how do you go about formulating it?

Last night I realised there was something that I was very frustrated with and it made me realise that there could be a gap in the market for that product (its e-commerce clothing).This morning I looked around to see if there were any competitors. There were a few (as it is a niche target audience) but I could not see why if I developed something similar it could not do as well or better (I was not impressed with competitor brands in this sector to be honest)My head is racing around with various ideas but I don't know where to start as I have never made a business plan or done market research before.Can anyone reccomend a series of steps in how to tackle this. i.e do I start by getting information on the target audience, then looking at competitors? Do I then try to look at competitor financial statements to see if its profitable etc.I guess I need to write a business plan but just not sure how to start this rather daunting market research.Thanks see hubwealthy.com/wealthy