Only through experience i found the drainholes on my D9 had blocked causing water to seep through the felt like seal on the sunroof, over the inner guttering and down the side of the drainpipes. ( the car parks with the front end pointing down, not through choice either ) Easy enough to fix all it takes is the removal of the A-panel trim, which is a clip on job but these clips aint destroy on removal oh no, theyre good uns,
the removal of the hand grab on the roof theyre pretty much straight forward, the two end pieces move inward to the middle of the handle itself, they havent got a slotted hole so they stay attached to the handle itself, a lever on the outside edge soon pops them off,
and the sun visor being careful of the vanity mirror lighting cable work, i didnt disconnect the cabling i couldnt find a plug so i left it balancing on the steering wheel to take the weight off the cables, though im sure a bit of tape up the window will do just as well. then carefully peel back the door seal end flap that lays over the top of the headlining, ( its gonna sound dirty, if not already ) then insert your finger or something clean and pointy between the headlining and the flap of the door seal i apologise for my method of wording this
, anyway run ya point-ed device down the length of the door seal to free the headlining. Carefully pull down the headlining and you will see in the front corner of the sunroof apature theres a black pipe, looks like an oil breather hose that fastens to a hose tail moulded to the sunroof opening, the pipe actually runs from there down the a-panel into the bulkhead to another hose tail, and from there...well i didnt follow it that far but i imagine inside the wing an down to the floor. To clear the pipe out if it is blocked i removed the pipe sunroof side as the bulkhead side looks impossible to get back on as its down the side of the dash where the a-panel trim disappears to. So yeah removed it sunroof side and blew down it... it definetley was blocked and gave me a sodding headache in trying, praps using a bicycle pump or something instead ? oh while your there ( wink wink ) and the headlining is down check the routing of the pipe as mine was routed in - i think - wrong as it had a kink in it where it was pinched against the sunroof mechansim, to rectify this get a hairdryer, be sure not to ask permission for it as you WILL NOT aquire it, sneak it outside and warm the pipe up the kink will eventually disappear, it helps heating the pipe to refit to the sunroof hosetail as it can be a bit of a swine praps even grease up the runners of the sunroof if ya got time to while the headlining is down, i did 
as the saying goes - refitting is the reverse of removal. All i would stress is take your time as its your headlining your dealing with, a nitemare if its shagged or the backingboard is broken as its been bent outta shape too much. if ya got rain marks on the rooflining like i did, i used carplans autovalet mousse with the brush on the top, sprayed it on but dont use the brush as it rags the headlining, i used a dishcloth and worked it in and - i spose chased the scummy ring the water left away then dried it with the smuggled hair dryer. Job Done ! all dry and smelling of citrus fresh and wd40 there we go, war and peace on leak faultfinding - apologies for no pictures on the subject, it was funnily enough raining at the time pretty easy job to do though, just be patient with the headlining part.