I logged on at 5.59am. 127000th in the queue, and now I find that if i had logged in ten minutes before, I could have checked out, done and dusted. That's just not on if they've advertised slots open at 6am.
I then sat for an hour and 2.0 mins, and when I got down to the last minute I had the thing in my hands ready to go.
I pressed the button to log in and select a slot when prompted - instead the fucking thing next showed me a page with the words nobody wants to see "you've been inactive for over ten minutes so we've given your slot to someone else, you'll have to join the queue again". 
I was bloody furious, three hours sleep and almost an hour and half wait and then that.
Rang them up and their customer "service" rep claimed three times there were no issues with the website - despite having an upset customer on the phone who clearly had had a huge issue. Said there was nothing she could do. I had a little cry and a swear.
By the time I got on there was nothing left.
And now I find out if I'd gone in via the app it let you skip the queue
I've really had enough now, I've spent thousands of pounds with them this year and this is how customer loyalty is repaid. I'll be moving supermarkets. The customer service rep didn't give a toss.