A roof over our heads

I have finished replacing the various broken and chipped tiles on the roof - a bit hesitant at first about using the angle grinder, but it worked like a charm, and now the edges of the rain gully are neat and tidy. I had been taking the old ones down and using them as patterns, but still had to cut three again. Our roof, in common with most others, has metal rungs attached over the tiles to allow easy access in winter to the ridge for snow clearing. On my various trips up and down, I wondered why, where the metal rungs were set under the flashing for the chimney, was what appeared to be a supermarket plastic bag stuck under the rung and the flashing. On my last trip up, I though it might be wise to investigate more thoroughly, and it turns out that the previous owner has obviously been employing that well known firm of builders Messrs Bodgit, Quick and Run. Where one of the metal rungs is set just under the flashing, its weight had cracked the tile. Rather than replace the tile, which meant taking out half a dozen tiles, unpinning the rung, cutting the tile as it was near the chimney etc. they just wedged a plastic bag under the rung, over the crack (which was more like a hole 2*4 inches), and hoped that under 2-3foot of snow it wouldn't leak. Having surmised that these were the same firm that probably built the Titanic, I set about the repair, which took a little ingenuity and some swearing, but was not difficult. I have no idea how long this has been in place, as I didn't recognise the plastic bag, but next spring I'll have to do further investigation to see how bad the water damage is underneath. Of course it was the third row from the top, so water was running down under the tiles from there, but underneath the battens is a waterproof membrane, so hopefully not too much damage. It makes me fear where else short corners have been taken...