to think shops and business should not be using aircon while we still have covid-19 circulating?

[Chicchicchicchiclana]

Yes, it's very hot and uncomfortable in many places right now.

But I was paying for my shopping in my local Co-Op last night, at the self service tills, and there was a whacking great aircon unit in full operation directly above where everyone was queuing/paying.

Am I wrong to find this very counter-intuitive? The shop is pretty cool because of all the fridges and doesn't have a large frontage facing directly into the sun or anything like that.

Hospitals aren't allowed to use air con or fans - dp works in the maintenance dept of a local hospital and he is always fixing/delivering/moving fans and AC units in and out of wards and rooms.

Where there is a lot of heat generating machinery you are going to need to cool the air (shops with large machines and even hospitals) but for general offices and areas it isn’t advised to use fans or air con and to have all the doors and windows open instead. It’s going to be a hot summer for some

Hospitals most definitely do use aircon. They have very precise targets for the indoor climate, especially in operating theatres, ICU etc. The humidity is controlled and there are rules and regulations about filters, and how often the air is refreshed. (I'm basing this on several countries in Europe - I'm presuming the UK is at least as good).
And there is a LOT of information on how HVAC systems do spread the corona (and other) viruses. It's been known for years. The Belgium government released another paper only yesterday, directly referencing the Covid-19 outbreak. Badly maintained systems, systems with insufficient filtration, and systems using recirculated air can all pose risks. As will any building with a too low humidity, which is one of the major risk factors. Hence hospitals keeping a relative humidity of around 50-60%.
Google Dr Stephanie Taylor. She's written a lot on the subject.