What strange reasons for not going to a site,

It’s not a strange reason at all. It’s personal choice. If I can choose between a site infested with rats and ladybirds and one that isn’t then why would I choose the one that is?

No idea why you would think the site to be infested with rats. Did any run over your feet? Many sites have baited rat traps in particular locations on site. The site is in the midst of rural fields and of course there are rats about. Why would there not be?

The warm weather in June/July year doubtless saw insects thrive in some areas and also their predators such as ladybirds. The Asian Harlequin Ladybirds which are now common are noted for finding somewhere to hibernate indoors in October. The native ones survive winter outside burrowing under leaf litter etc

https://www.theguardian.com/environment/shortcuts/2018/oct/11/invasion-of-the-ladybirds-why-are-these-sti-infected-insects-taking-over-our-homes

Try just sucking up the Harlequin ones if you identify them as they are parasites to our own native species and will cannibalise them. Seriously.

I do think you have to take the exceptionally hot summer we had last year as a reason for this irruption. We have experienced several different irruptions (caterpillars/flies/beetles) when abroad but upon returning to the site a few years later didn't experience the same problems. It's nature.

No idea why you thought I said the site was infested with rats. There were rats on the site. We watched them. I suppose they could have been escaped hamsters but why would the wardens get the council out to put hamster traps around the site.

Hamsters? Where did they come from?

No idea why you thought I said the site was infested with rats.

Maybe because you posted:

It’s not a strange reason at all. It’s personal choice. If I can choose between a site infested with rats and ladybirds and one that isn’t then why would I choose the one that is?

On a number of sites I have observed traps 

why would the wardens get the council out to put hamster traps around the site.

They would not get the council in. Maybe Rentokill or buy professional type bait stations and warden place and replenish bait. For example I noticed that at Southport, behind one of the toilet blocks with waste collection area nearby, there were several in the fenced off area behind the block (bait boxes not rats that is ).

Many that are kept are from desert areas in Asia and Syria originally.