Pannier fitting help please

Hi all,
I've recently bought myself a G650 GS. I also managed to buy, separately from another seller, a top box and a pair of BMW panniers. Can anyone pleas advise what I need still in order to fit said boxes.
I've so far fitted the rail bars , which I believe the base of the boxes slot onto to. I am missing the mushroom bolts, which I think may be all what is required. I also have a selection of bolts and another bar thing (unsure what this is??). Am I right in thinking buy mushroom head bolts, remove plastic circle cover, remove existing bolt and fit said mushroom bolts for the top of boxes to mount on?
Thanks in advance, please see attached images

Base rail bracket fitted-
https://imageshack.com/i/pmQx1QB1j
Panniers I have-
https://imageshack.com/i/pml3AINAj
https://imageshack.com/i/pniNI9aPj

Bits and pieces/bolts etc-

https://imageshack.com/i/pmoLkyY2j


Bar- unsure what this is?
https://imageshack.com/i/pn3bBenBj

AFAIK - on the 800 GS The "mushroom" bolt fits in a welded stub on the top pannier rail, the bar you ask about looks like the original grab rail which will be redundant. I tried to insert a phot of the set on mine but cant manage. the attached phot is in the gs section. You can see the silver "mushroom" bolt in this phot.

Might get a better response in the correct section - http://www.ukgser.com/forums/forumdisplay.php/79-650-amp-450-singles

HTB1 said:

AFAIK - on the 800 GS The "mushroom" bolt fits in a welded stub on the top pannier rail, the bar you ask about looks like the original grab rail which will be redundant. I tried to insert a phot of the set on mine but cant manage. the attached phot is in the gs section. You can see the silver "mushroom" bolt in this phot.

Click to expand...

Thanks .looking at the panniers, the mushroom before lt would need to be almost upright rather than sideways. My local non-franchised has Ordered two, hopefully that'll do the job!