Airline travel regulations in the United Kingdom are less strict about taking baby milk and food quantities for babies on plane flights.
FLIGHT ALLOWANCE FOR BABY FOODS: If you are traveling with a baby on an airplane you are permitted to take enough baby food, baby milk, and sterilized water for the entire journey.
The amount may be over the normal 100ml liquid limit in some cases.
Airport staff at the security point may need to open the food and milk containers to screen the liquids.
Please take note that airport security regulations change regularly.
All of the following items are allowed in your carry on hand luggage and inside your hold luggage:
Note: You may face restrictions of 100ml for products like baby lotion or nappy cream (carried in a clear bag).
Even though the UK Department of Transport presently restricts the quantity of liquids being taken through airport security control to 100 ml, the same rule does not apply to baby milk and baby food.
When you take a flight with a baby you are allowed to take baby milk and food in much higher quantities.
As a rule you may take as much baby foods as you need for the flight although you should be prepared for delays for longer customs checks.
You may also need to verify the liquids by tasting them yourself so you might need to open sealed cartons and jars. The foods will usually be confiscated if you refuse to taste them.
You can normally buy baby food and milk after you get through security. Stock on the shelves are pre-screened so you will not have to verify these yourself.
Some airports operate a reserve-and-collect service for formula milk so you can book your chosen brand of formula with your airline and collect it at the departure lounge.
Baby Food Allowance and Milk Restrictions; UK Rules Updated 2017