Can stress affect your Diabetes?

Yes, stress definitely sends your blood sugar levels up. Mine go up whenever I have a hospital or dental appointment, in the past whenever I had an exam, when I was moving house, when I had to give a presentation at work etc. Anything you are stressed or anxious about sends levels up.
Basically, if your brain is viewing the situation as am emergency, it will cause your liver to supply extra glucose from storage to give you the extra energy for physical activity. These days, however, a lot of what we are anxious sbout cannot be sorted out by a quick burst of running or a fight, so if we can't produce extra insulin to deal with the extra glucose, our kevels end up higher as a result. Hope this is helpful.
I've no experience of the Low Carb programme personally.

Stress and illness can raise blood sugars.
Our bodies notice the stress and send a message to our livers to release glucose to provide the energy to fight the illness and deal with the stress.

With regards to the Low Carb Program, yes anyone can join, there is a fee £14.99 per month or £69.99 for a year.
However if a GP or other Health Care Professional feels it would be of benefit for you they can prescribe it by providing a code for you to register for free.
https://www.lowcarbprogram.com/

Edit for typo

My levels went up when I was stressed at work for sure. Took the decision to retire early and stop working Although that presented a financial challenge and still does, better that than risking your health

Yes both short and long term stress can affect our glucose levels. And as already mentioned other issues such illness, pain, some medications... etc, also affect our glucose levels. it's just nature's way of preparing us to deal with different or difficult (fight or flight!) situations. So it's not just what we eat that might cause a rise.

I was already eating a low carb/ketogenic diet well before the Low Carb Programme was introduced, otherwise I might have considered giving it a try. I think it's a useful tool for people wanting or preferring a more structured introduction to lower carb eating.

Definitely I would say it does. As soon as I de stress or try to, it will jump back down to a normal (for me) level.

As others said yes it can have a negative impact on blood glucose levels.

Personally I am a believer that some stress is beneficial as it boosts our immunity, sharpens our cognitive thinking and keeps us focussed, however long term stress is not good and living with it daily is unhealthy, so trying to pinpoint the cause of stress and looking at ways of managing it are vital. Things I do when I find it's impacting me negatively are exercise, meditation, good sleep patterns, healthy diet, reducing alcohol intake, all help me manage and cope better with stressful situations. Personally I don't believe in avoiding stress as it's virtually impossible to do so or taking medication, but being mindful of it and it's affects on our blood glucose levels so we can cope better with it.