Till you pull it all out you won't really know if you can make the bend to fit the gully to the ic. It looks tight. If it's only rainwater and softened water going in you could use a back inlet gully. Connect that one to the ic, maybe even where you want your softener, then connect some 110mm into the back of that gully and run it to the corner where you want this downpipe to finish.
Might be even easier to keep gully where it is then used some dished channel drainage or similar and put a shoe on the bottom of downpipe