Barsel, I got an email from Sainsbury's Customer Services when I did the same as you.
//Thanks for your recent email about our non sale of fireworks, we are deeply sorry for any time in taken to respond to your email,
We aim to answer all our customers as quickly as we can, on this occasion we have logged this with our trading team to ensure they receive your feedback on the non sale of fireworks, we are glad you are happy with this, and we value your feedback,
We appreciate you taking the time to contact us and we do hope to see you back in store again soon
Kind regards,//