Terrain 100mm / 4 inch half round guttering Parts still available?

[raindancer]

I live in a terraced house (row of 3) and the guttering front and back is brown plastic Terrain 100mm / 4 inch half round. The unions , end caps and running outlets are all leaking and i'd like to replace them but it seems impossible to find the right size. Everything seems to be 112mm. Can i use 112mm on my part of the shared gutters or should I talk to the neighbours and start thinking about replacing the whole lot?

 

[Exedon]

Terrain was bought out by the Polypipe group some years ago .
Most lines were immediately abandoned and they stopped production completely about 3 or 4 years ago.