Ofsted is compulsory. Go to their website for info and fees, it is quite good and not scary.
Ncma is optional, about £30? I cant remember all the fees, again they have a website.
You need third party insurance (ncma's version is £20pa)
You need specific car insurance if you are going to use a car (mine was £100 more expensive than ordinary insurance).
You also need a health check by your doctor which can be up to £100
You need to do a pediatric first aid course, allow £90.
You need to do a basic childminders course called an ICP (which is also unit 1 of the Diploma in Homebased childcare) and funded by local council.
You may get a start up grant from your local council to help pay for these things.
Being self employed you need to inform HMRC (tax office) as soon as you open. You pay class 2 NI which is about £30 every quarter and they send you a bill by post for it. Then if you make a good profit you pay class 4 NI as well. This is calculated by the tax office at the end of the year and charged to you along with your tax bill.
There are lots of expenses you can claim. For a car it is 40p per mile or you can take 10% of the cost of the car per year. You can claim up to a third of your household bills (gas/electric), and every thing you use from enterance fees to groups to toilet rolls. There are some exceptions - you cant claim for the Birthday presents you give to the children.
Since you have a CRB then it really depends how soon you can organise the First Aid and ICP courses everything else should be fast. Then you can open. Ofsted do an initial inspection within 6 months of your opening date then drop in every 3 years.
Getting your first client can range from immediately if you have friends who need the service to 13months (is the longest I've heard of)on average 2-6months. Then another 6 months to be reasonably full.
Its a long process and if you thought teachers had long hours doing stuff in the background, just wait until you see what childminders do. My hours with children here are 8am-7pm then cleaning, planning, resourcing, paperwork, admin, training courses,etc etc stretch my working day 6.30am to 10pm. Plus 5 hours at the weekend doing the EYFS