I've found the best way to complain about any council department is not to bother complaining to them directly, but by phoning the town hall complaints department and telling them you would like them to send you the paperwork to make a written complaint.
Get all complaints in writing and make sure you have a record of who you have spoken to and the times and dates.
Email as well.
I got my complaint acted on satisfactorily within a day without them sending me the paperwork. Councils don't like written complaints cos it leaves a trail.
If you want to make their day, complain over the phone. They will lie and deny at a later date.
Always start your telephone conversation with, "who am i speaking to?"
Also worth contacting your local mp office. Especially if the mp is from a different political party than the council. But they will ask you for basically a log of what/when you did and who were you speaking too.
It will be too late for this contract but if nepotism is at work a written complaint sent to various members of the council will mark their cards for when the contract comes up for renewal.
Go for it and the best of luck. But it might harm your chances of future work if you manage to get someone fingered.
To summarise:
town hall
local mp.
There is a local ombudsman as well if you don't have satisfaction from tthe council.