I’d always used Ocado for years, but when it changed to M&S I had constant problems. Occasionally I’d check in and find a random next day delivery slot, reserve it, do my shop and then find the screen freeze every time I tried to click my saved payment details. Then funnily enough it would empty my basket and the slot would be gone. When I have managed my order 25% of it would be substitutions. Have now changed weekly back to Waitrose. I hope Ocado read all these bad reviews as I love the M&S choice but I refuse to use Ocado whilst the service has been so bad.