dont let him near the car, i think your being seriously shafted here!!!!!
get to a iron mongers, buy 4m of net curtain wire (about £1.30) wind the sunroof back, check rails and drain holes...
is there water closhing about up there ???
run wire down the drain holes, push the caps open (there are rubber end caps to stop bugs crawlig up the pipes, but they get blocked with all the crud leaking through the felt around the edge of the sunroof)
if no joy getting the blockage cleared. take the inner arch off the back of the front arches, remove the black end caps on the end of the white pipes.
do same for rear ones.
use hot water with lots of washing up liquid to flush the drain holes/pipes clear of anymore slimy gunk.
if all clear then thats the cause of the water leaking into the interior.
just a case of mopping up and draining the water under the carpets (pop the plugs in the floorpan to drain it out).
do a search on here for leaky sunroofs.
its a common problem if you still have the annoying end caps on the drainage pipes, ive had it on both lagunas this year!
hehehe £800...... i'll do it for £200 (and drive all the way from east anglia to your front door to do it as well)
though im sure one of the senior members on this forum will undercut me by £150+ if your near them...