Thanks ever so much for your advice on writing. My plan at present is to finish the first draft, then revise it, go through it again with a book I have on self-editing (written by two professional editors) and then put it to beta readers. I know I'm too close to it and won't be able to see where it's going wrong myself. One of them is my best friend of 30 years (I recently beta read for her) who I know will give an honest opinion without agenda and that criticism will be constructive. The other I'm hoping for is my former English teacher but that's dependent on whether I'm able to track him down and whether he wants to do it! I'll consider their comments, make any necessary changes and then submit it to an editor. I'm definitely not going to be picking one from an advert, I'm going to get some recommendations, look at their credentials and then get ones I'm considering to do a sample edit before I decide who to go with. I'll then brace myself for having it pulled apart! It's a lot of steps to go through before publishing but I want it to be as good as it can be.
The competition and market part is definitely a weak spot as I don't know for certain where it fits in, I'm hoping an editor will be able to clarify which "bookshelf" it should sit on. Because of that, I'm unsure as to who my competition is. I'm writing a story that I would love to read and that people I know will also love but on a wider scale I don't think it's a lot of people's cup of tea. That's the main reason I'm self-publishing, I don't think any publisher would touch it with a barge pole regardless of how good the writing is.
Thanks for all the help and advice, it's very much appreciated