Dormers is around 1300 tall.
I'd push tiles up on the roof and work from there .
Leaning the ladder against the vertical isn't a good plan . They will all be nailed and a pain to repair properly .
Second option as already suggested work from the flat roof
There are several suppliers of cast iron gutters online .
You can usually ignore the next day delivery claim .. it's never happend to me . Usually 7 to 10 days.
Or a decent roofing merchant should be able to get in what you need ..
they are all nailed thats why you need to do the whole hip. The nails will be failing.
I would expect you may find a guy who would stick them in with a bit of g fill. Hopefully any of the others dont fall out and hit your kids , you now know , its unsafe and needs dealing with
they are all nailed and bedded . if some come out then expect the others to follow in the future.
id have them all lifted re drilled and re fitted from bottom to top.
for replacement hips you'll need roof pitch, looks about 35 degrees but that's a guess
the lower damaged tiles are probably end...
By the time you messed around doing a temporary fix you could do it probably by replacing the tile .
They look like Marley moderns very easy to replace .under a minute
Btw there is a leak . The underlay is picking it up .for now
You'd need to re hole , and they likely not sit good. And you would need to cut to get the bond .
Bonding strip would work .
You can get cement fibres in 250 x 500