Roof concerns?

[DonkeyKong01]

We are a semi detached and a few months ago our neighbours had their half of the roof replaced (first we knew of the plan was when the scaffolding went up)

Last week a tile on our half (where the roofs meet) slipped down leaving a hole that needed attention. Our friendly roofer neighbour went up long ladders to fix it for us. He suggested that the roofers on the new half hadnt fixed our tiles in properly where the two meet which had caused the slip.

Now... looking at the tile line from the garden, the tiles don't appear to meet the line (plastic looking edging stuff) that separates the two roofs the further up the line we look (meet at the bottom but misaligned further up? (Apologies, I don't know all the terminology!) Should we get this looked at? Who by? What would the answer be?! I'm feeling quite worried about longer term problems that may be caused.

#NoClueAboutHomeCare

I'd ask a qualified roofer to do a report, even if it costs you.
Then check your home insurance policy to see if you have any free legal advice. If not, then send/give a copy of the report to your neighbours and point out the problems. Their roofer should have at the very least made sure there were no gaps or unsecured tiles adjoining their work. That's really poor workmanship - I'm alright Jack attitude.
It may well be that your roof is in desperate need of attention and the neighbours work has highlighted this.
Your roof is one major thing you can't ignore. Water ingress can cause all sorts of problems.

Thank you @TheSilentSister! That's really helped. I'll get onto getting a report so we know what's what ☺️