Neighbour started selling cars form home. Nowhere to park.

[Oblomov]

Obviously not a crime. But we live in a close. Garages which people park infront of. And a bay, where people park. None of them are allocated in any way.

Round the corner, more houses, with unallocated spaces. Then on the corner of that, a block of flats.

Bloke from block of flats has started selling cars. Has parked 4, in our bay that has enough spaces for 6.

It is a bit cheeky, isn't it ?
What can you do ?

Def do what Seeline said - I'm pretty sure it is an offence - something to do with licensing for street trading (it's unlikely he would have been granted a licence for something that interferes with enighbours' parking). Council is the first stop - trading standards or licensing department. Our of interest, whereabouts are you?