I was looking for some info on interior lighting and found mainly questions, Its taken a couple of days, but I've finally come up with something that might help others in the same boat.
(http://s30.postimg.org/4bs1quawx/lamp.jpg)
Its not perfect, the lower shade rim is still a little patchy, but that could probably be fixed by increasing final gather in the render quality settings. As it is, that scene was rendered with a FG of 12 -- heres one rendered at FG5
(http://s29.postimg.org/7uzqs1sjb/problem1.jpg)
And heres a cross section of the model
(http://s8.postimg.org/lgxaxxh39/cutaway.jpg)
I don't know if this is the best/easiest way to do it, but it might give an idea to someone else who's struggling.
At 12mb I've had to split the attachment, but theres also a copy here
http://www.filefactory.com/file/7f1xipvwy7ml/n/table_lamp.ksp (http://www.filefactory.com/file/7f1xipvwy7ml/n/table_lamp.ksp)
PM me if it dies and I'll up it again)