First off you need to take a bit of a reality pill! being self employed and building a business from nothing will take all of your time and all of your energies.
First you need to look critically at your skills and identify where the gaps are. so for example could you do your own tax return or would you have to pay someone to do it for you?
Then you need to make a decision on what type of business you want to run. if you are running one from home, how much space will you need? would it constitute change of use under planning laws? where would you store things?
Then and the most important thing of all, you need a proper, costed, honest business plan. Fail to plan, plan to fail!
Start making contacts now with people like FSB, women in business groups etc. there will be loads in your area and you might get some free advice or support sessions as part of your membership.
but please don't even think of starting a new business without a business plan. so many people do, they pour in time money and energy and they fail.
a business plan will help you to research your market - are you a new type of business in the area or a "me too". it will identify your USP's where your own skill shortages are, what courses you need to go on - like food hygiene, health and safety, resuscitation etc.
Its really, really hard to earn £40K self employed.
usually with business start ups people go for the something they have worked in before or something that they have as a hobby or are passionate about. just not feeling that any of your ideas fit into this.
message me if you want any more help/support.