Well, I'll skip the opprobium, and try to be helpful!
If child is 4+, I guess s/he is in reception, rather than trying to get into a school?
You would have to be clear as to what you were tutoring for. Does he have fine motor issues, making writing hard - would he benefit from a good OT, who are the best route for fine motor, problems sitting still etc at that age. Do you feel he is behind in reading, in which case working on his phonics yourself is likely to be the best route, unless you think there is some underlying developmental issue in which case you need different specialists.
To be brutal, if you just can't be bothered (:-)) to do the extention reading and number games that many use to coax receptioners along, or push them to the top of the class, depending on one's viewpoint and style, you may be able to get someone else to, but it mightn't be easy. I think most of the big agencies would hesitate to take on receptioners unless they had a clear problem, as suggested above.
If you are thinking of tutoring at this age to get ahead for 8+ it is truly too early (although I do know of a boy tutored from class 1 for this purpose).
EducationCity is really fun, and BBC bitesize KS1 (if you can bear the accents used) seems to go down well too, if you are just looking for some extension.