Stopcock and earthing point access.

No. Must have seen this a hundred times. You need access to both.

Hi, im guessing the stop tap is behind the vanity unit panel, if it is and you have a good idea where the stop tap is you can make a round hole with a hole saw around 50mm that should give u enough access if you ever need to turn it off. If you do try it yourself use ur drill on slow speed and low force once you have made try not to use a pilot bit instead use the hole saw at an angle to start off with. last thing you want to do is damage the piping.

This is totally care less action , stopcock has to be accessible and easy to reach for any one in case of emergency leak or other accident with the water supply in the property , earth bonding is not that great mistake as most of the new main supply pipes is plastic pipe , but its good practice to have earth pounding at every pipe specially gas pipe . So yes stopcock is the problem that need to look after .

No . Its liveable as long as you have access to your outside stopcock but not advised

No

Definitely not

you should have used a qualified plumber not a builder.