Hepworth Plastic Bottle Gully? Any ideas how to access the pipe to clear a blockage?

[Egnaro]

Had a Boxing Day blockage from the kitchen sink gully.

 

Gully was fitted in 2002 and no longer available, I can find no info on this gully. Pic of cover and under cover if it helps.

 

 

[Russell griffiths]

Stick your hand down it and yank out that black thing, I think it comes out. 

[Egnaro]

With the two spigots on the inside? 

[dpmiller]

yep, that is the "bucket" that makes the gully a trap.