Yes, I know these have been done to death and yes I have googled!

There seem to be a miriad of products for flat roof repair, but there also
seem to be numerous materials which have been used in the construction of
these. I'm hoping someone can point me in the right direction for repair of
mine.

The main covering of the roof is a dull silver grey matt finish with no
chippings, aggregate, sand or other additives.
This is sealed around the edge with the (more common I think) dark, grit
covered variety.

The problem appears to be that the main grey covering is splitting along the
length of the roof (perpendicular to the roof/ceiling joists) in neat lines
which are spaced between 18" and 30". These splits are upto 3mm wide in
places.

I intend to replace the roof with pitched version, but would like a repair
(if possible) that will see us for 1-2 years whilst we attend to higher
priorities.

Is this possible?
If so, what is the best product to go for?

TIA

Phil