Ask HN: UK Local Council GDPR Breach Advice?

Due to COVID, a consultation on the location of a secondary school campus was held entirely online by my local Council in the UK. It has been contentious because there were five options and the Council's preferred one involved sacrificing a local greenspace/park.

They concluded that the silent majority preferred their option because the site received 1500 visits and 70 objections (preferring an alternative) versus 20 non-negative comments.

They are using this 1500 number to justify their position. I'd noted accessibility issues (the site says certain user agents are incompatible and you can't view the site at all)

That in context, the site itself had a cookie splash screen asking to accept or reject cookies for analytics. Upon viewing the source code I noticed that the buttons were the wrong way round, i.e. those who rejected cookies were being tracked those who clicked accept were not being tracked.

Is this a clear cut case of a GDPR breach and the information collected should be thrown away? I have sent relevant information to ICO but wondered if the wisdom of the HN crowd could offer further info.