Vent pipes

[tommyt]

Pondering my waste pipe vent connections. 
Only place I can go out is above the bathroom. 
All bathroom wastes except WC will go down into ceiling space and connect in the utility room below. 
the WC will be above the floor to the corner of the room where the 110mm can come up through. 
Just wondering if I can have the vent after the WC connection (B) or continue it up where the branch to that pipe is in the corner? 
Also can the vent be 50mm or will I need to make it 82mm

 

Also the kitchen soil pipe has been put on a y branch under the B&B floor so assume it won’t need a vent as it’s connected to the same stack that will get a vent?

 

please see fag packet sketch