Send a written complaint. this will make them aware that you know your rights and are willing to take legal action if necessary. collect any evidence that can help to prove they're liable, such as photos, dates and correspondence. find out whether they're in a trade association that has a dispute resolution scheme.
if still failing to do so, trading standards may be the next step, they’ll look into the company that’s in question, and they’ll get everything you need, if they’re still noncompliant, your in your legal right to get another tradesmen to take a look and quote you on this, you can then forward this quotation to the company in question, if still nothing you can then get a new company in to complete the job, you can then take the original builders/contractor to a small claims court to which you’ll be compensated the costs of the works carried out.
regardless of what your neighbours and the builders are saying, your property should be left the way it has been, by all means mistakes/accidents happen, any professional would rectify any problems they’ve caused,
i hope this helps, and hope you get the issue sorted promptly,
kind regards,
prestigious maintenance.