Not sure if it's everywhere but I use a volunteer group called "Covid-19 Mutual Aid" I rang them weeks ago explained that I wasn't in the shielding group but had to be stringently social distance as per the guidelines and they gave me what has become my own rep of sorts who goes shopping for me. So it might be worth googling your area for volunteer groups. The guy has been brilliant and just calls me when he is going shopping. £45 limit of sorts and I just send him my list via email and pay the bill into his bank account so it's very easy.
Click and Collect slots are becoming more available as well as
Brunneria says although my local Sainsbury it's about a weeks wait. Was quite nervous about it to start with but it's great. Order online and you can change your order until the night before. Drive there, pull into a slot, they call out your name and someone leaves your shopping fully bagged by the boot. Load up and drive off. Really good actually.