Joining odd sizes of guttering

[halfmarathonmike]

Folks, after youe advice

I've just replaced all the iron guttering on the back of the house with new wicked pvc guttering - the issue has come when I've tried to connect to next doors (terraced houses). My neighbour seems to have a similar shaped half moon shaped gutter (112mm dia.) but a larger diameter. Is there such a piece to step different guttering sizes?

 

[HERTS P&D]

Are they both 'half round'? If so then cut a small section off the bigger guttering to fit the gutter union.

Andy