Found a PDF on a rail trade website detailing Standard Premier service: essentially no more hot food, no more champagne, and only one free drink:
30-minute check-in
Dedicated fist class carriages and dedicated staff who welcome you onboard and are there throughout the journey to assist.
Light cold savoury meal consisting of 3 "tasting" dishes and drink at seat (see catering section)
Magazines on board
Power points at every seat (both UK and European compatible)
Comfortable larger reclining seats in air-conditioned first class carriages.
Meals served reflect a range of fresh and healthy international dishes and are appropriate to the time of day. Only Business Premier and Standard Premier customers are served meals at their seat. Breakfast is served until 11:00, Lunch: between 11:00 and 14:00, Afternoon meal: between 14:00 and 17:00 and Dinner: from 17:00.
Breakfast - Bread roll, pastries and orange juice. Tea/coffee.
Lunch - Light cold meal consisting of 3 small savoury "tasting" dishes. Served with bread.
Afternoon meal - Light cold meal consisting of 3 small savoury "tasting" dishes. Served with bread.
Dinner - Light cold meal consisting of 3 small savoury "tasting" dishes. Served with bread.
Drinks - 1 complimentary hot drink, soft drink, small bottle of wine or beer.
Link to full PDF
here