What Pete says is very true. A drain appears to pass water, but how much? A partly blocked exit can cause the water to back-up, up to eye-level even (!), and the channel area of the sunroof fills very quickly if all drains are not 100%. Water then gradually seep/pour through the joints at the rubber grommet end, or worse still overflow through to the cabin above your head. The white tape on the drain hoses is NOT a sealing device incidentally. It was applied by the factory to aid fitting (just showed how far the pipe was to be pushed into the rubber duck-bill grommets).
Although obviously possible, I doubt that windscreen seal-rubbers are the problem, unless the windscreen has been replaced and fitted badly.
You really should go back to the drains and follow the instructions in this extensive thread from Nick at Austin Garages:
https://www.two-sixties.co.uk/mgoc26...plete-Solution
Best approach having cleaned and trimmed the rubber grommet duck-bill ends, is to use an adapter like Austin garages sell.
IMG_3686.jpg
https://www.ebay.co.uk/itm/194376080...cAAOSwLVdgFq--
Read the information there as well, although much is an extract from his Forum blow-by-blow instructions, mentioned above.
The things are fairly standard barbed hose connectors/reducers which you may be able to source locally. 10mm>14 mm measured at the straight part not the barb OD.
I would advise to modify both the front drains, and those at the rear of the car too. they may not leak yet, but probably will at some stage. The rears are a much easier task than doing the front drains, incidentally.
Another possible area causing leakage is the windscreen shuttle panel, the exterior one through which the wiper-spindles pass. The 7 fixing pin 'receivers', or snap-sacks, can leak.
See: https://rimmerbros.com/Item--i-GRID001775
Best to replace the seven exterior windscreen shuttle panel push in retaining pins or clips, items #7, Clip EYC101470PMA, and #8 the Clip-Snap-Sack EYC101450
Most important is to fit the new white recipient 'snap-sacks' with a sealant to the body (not in the central pin-clip hole of course).
The Snap-Sack part is common to some Range-Rovers (2002-2012), and may be more readily available locally. Same LR part number I think.
David