It isn't my personal opinion, it was discussed fairly widely. If you look on e.g. Welsh govt guidance it explains that toilets carry a risk (unlike e.g. standing outside).
Ok so the Welsh gov guidance say 'Toilets are potentially a risk for transmission of the virus if not managed well.'
That is not at all the same thing as
*'a particular area of concern' as it is often the only indoor bit of a day trip out/visit to venue and thought that is where a significant number caught it'
Which is what you said. I also can't see any Welsh give stats stating that toilets are a significant cause of infection. Could you link to this please or is it just your opinion?
Toilets are often small rooms. Sometimes there is more than one person in at a time.
Not generally in a toilet cubicle 
There's plenty of scope for social distancing and cubicles are partitioned, just like cashiers at the supermarket.
People breathe whilst using the toilet. The next person comes in and breathes in what was breathed out by the person before.
How is this different from a supermarket queue? Or any other indoor area.
Also people touch things in toilets.
I think this is why handwashing is encouraged
These things are so obvious that I don't understand why you are questioning it.
I haven't actually questioned any of these because they weren't part of your original statement. I'm reasonably familiar with public toilets so tbh your descriptions of them as small rooms where more than one person may be, aren't as enlightening as you might think. You've made (another) incorrect assumption that I've asked those questions (you do make a lot of assumptions)
What I actually questioned was your statement that toilets are the place where a significant number of people have caught coronavirus.
Rather than just answer that it's just your opinion and not actually fact, you've instead gone to the trouble of describing public toilets for me. As I said, not as helpful as you think and also not what I asked.
You have zero evidence for what you said - there's no evidence that public toilets are a significant source if coronavirus transmission on days out. You've made it up based on you assumptions. And let's face it, your assumptions on this threads haven't exactly been accurate have they?
I find it strange that some people are so keen to present their own scaremongering opinion as fact. There is already enough misplaced anxiety around coronavirus. Why would you want to add to that?