London to Amsterdam by Eurostar : worth paying extra?

If this is the standard premier as opposed to the business premier then it is more of a snack than a meal (there is something else served after Brussels and there is rather more on the evening service than the breakfast one). As it will be their new train note that standard has electric sockets & free WiFi. Bar is standing only from the pictures.

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

No, it isn't worth it. But you might want to pay for the right to change travel time or day. And don't forget that assigned seats mean you want to wait near the spot your train car will be. Allow extra time, as they warn you, for pre-boarding immigration paperwork

Is it worth paying the extra fare for the wine/meal? (extra 40lbs)

No matter what they sell you on the Eurostar, you won't pay for it by gaining 40 lbs. :-)