GTV sunroof and algae/mould on seat

HI
I have just come from looking at a lovely lusso gtv that everything going for it including electric/heated seats and 17inch alloys but it has sunroof and their seemed to be green algae/mould in the creases of the seats.

This made me quite suspiscious.

Are the sunrooves(?) on GTV's reliable?
I assume the mould stuff is because the roof has perhaps leaked and it has got damp on the leather seats.
The rest of the interior was spotless but the garage had obviously missed cleaning in the creases/ribs of the seats.

Plus the seats were heated so I thought this may have contributed.

If there sunroof was defective and did leak are they expensive to get resealed?

lovely car and great price too

r