DIY Doctor UK DIY Forums

Just wanting opinions from people better in the know than myself.
I've worked as a labourer on and off past couple of years but haven't seen a roof done, start to finish.
The building i own a flat in, is having some major external works, including recovering of flat roof. Seems they're also redoing the tiled bit of the roof that leads onto the flat.
I was sent these pics by fellow leaseholder and want to know if i'm right to be concerned regarding:
1. No slate overlap on edge of the roof.
2. Surrounding tiles aren't overlapping the vent slates.
3. There doesn't appear to be vapour barrier or battens.
4. There doesn't appear to be very much overlap on any of the tiles.

Two companies submitted quotes for the job, the cheaper of the two have a presence online, the more expensive one i cant find a single mention of online, obviously freeholder went with them greased palms and the like, if the job was a decent job i wouldn't mind, but so far it looks rubbish, the bill for these works are significant and its allready leaked.
If could just add thoughts on the work so far.
Thanks in advance for help.

What I'd do is would post this question on multiple forums (there are many out there) and maybe social media.
You'll want to get loads of responses so that you can choose the best advise/technique etc

Thinking I should get some better pics first. Thanks for advice though WilliamNeat.