Hi,
Because you mention a Borough, I presume you are somewhere in London. There are loads of Home Ed groups around London.
My DD will turn 5 in January and so does not legally have to be 'educated' until Easter (the obligation starts the term after they turn 5). Seeing the headache so many have had chasing places at preschools/primaries, I'm jolly glad to be out of it. It is hard for us managing on one salary, but from what we have seen of DD and other HEdded children, we believe it is worth it. We started a year ago, at preschool age - and it has gone so well for us, we did not apply for a reception place.
It is worth checking out the websites for Education Otherwise and HEAS, to get contact details for groups local to you. Also worth seeing if there is a Yahoo Group for your area (I found them invaluable for asking/answering questions, as well as co-operative stuff).
I wouldn't worry too much about the 'how' as almost everything is learning experience at this age. I believe the two organisations I've mentioned do have helplines that give free advice.
If you intend to get your child into school on a different intake, you may find it useful to check the National Curriculum targets for your child's age group. This information is freely available online -although do bear in mind that as a Home Edder, you are under no obligation to follow the National Curriculum. I know of one business that sells primary-aged packs that follow the National Curriculum - PM me if you want details.
HTH