This thread has me completely bemused. OP has had the "official shielding" letter which no, is not the one from the government to all households, but is the one from the NHS to people with specific health conditions, otherwise she wouldn't be shielding because Shielding Is Not Fun! My household self isolated for 2 weeks because I had some suspicious symptoms so my employer told me to keep them to myself for the recommended period - don't think it was Covid 19 as it turned out, but better safe than etc - and that was quite enough no fun. Imagine being stuck indoors for 3 months, not able to even potter to the shops for yourself, with the added knowledge that you are more likely to die than most people if you do contract the virus. To top it all, someone close to you has very recently died from that very thing. Drama queen you say?
Yes, some people have had the shielding letter who don't really need it, some GPs being over zealous perhaps. I presume OP knows whether she falls into that category because it's her health that she lives with. We don't, and it's none of our business. Suffice it to say that she believes she is doing the correct thing.
Add to this that there are instructions from the government and protocols within businesses as to how these things are supposed to be handled. The driver clearly did not act with regard to either of these, nor to the OP's expressed wishes in writing, as she has explained, nor to her verbal request, although she accepts she could have been firmer about the latter. But then, should she really have to? There's a bloody pandemic fgs. Everyone must know this stuff by now.
Enough with the "well if you complain he'll be sacked and starve to death and there'll be no-one to deliver your groceries anyway" nonsense. The employer won't want to sack a key worker, particularly in these difficult times. Worst that is likely to happen is being dragged in for a bit of extra training, from which, quite frankly, he sounds as though he would benefit. If he takes protocol that casually he's unlikely to be in fear of death himself. And if he'd "just had enough" after a hard day, as someone else said, he'd be a bit grumpier rather than laughing and pushing in, wouldn't he? Not having to get close to yet another customer would surely be a bonus. But in any case, would that give him the right to take it out on the customer? OP has already said she doesn't intend to make a complaint anyway. Personally, I would, but probably as a pp did would not make it identifiable. It's not about getting someone into trouble, it's about making sure everyone is clear about what it is safe and proper to do.
Then we have posters questioning why OP has even bothered to make a thread. What? Why? Take a look at this topic. How many of those threads really need to be started? I'll take a wild stab and suggest absolutely none. And yet here we all are. OP has as much right as every other user of the site to post any query or complaint she wants to on it. Just letting off steam? Sure, why not? No, not everyone's going to agree, but some have managed to do it quite politely. Others have put the boot in. CUT IT OUT. OP is having to stay indoors for her health, but even if she were a complete hypochondriac her fear is real and should receive a modicum of decent human sympathy. Pick someone tough to get tough on if you must.