Info about Eurostar classes here: https://www.seat61.com/London-to-Paris-by-train.htm#Eurostar_classes_explained
The rest of that page has lots of other Eurostar info.
- Standard class is 2+2 seating
- Standard Premier is 2+1 seating with a small cold meal.
- Business Premier is 2+1 seating, plus a warm meal, plus flexible tickets (if you want to change your mind and get a different train).
Business Premier is designed for business travellers and is identical seating to Standard Premier. it is not a 40lbs meal, that would be too heavy ☺ ("40lbs" = 40 pounds weight, pound money is £40 or GBP 40). Not worth the money.
I would also say Standard Premier is only worth about £10-£15 pounds extra, if the difference is more, just go standard class.
Yes, there is a snack car on the train with limited seating, but most people take their food and drink back to their seats. It has a limited choice, a better option is to buy food at St Pancras station and eat it on the train.
There is a photo of the café-bar on the same webpage: https://www.seat61.com/images/Eurostar-e320-bar.jpg