On puppies it's actually fine for them to be from fit to a little plump and individuals vary widely anyway -- I found myself that they would go from one to another within a single day
simply because their bellies can look very full when they've just eaten and by the time that has gone through they are slender again!
Cathryn, who is an experienced show breeder, has given some good advice. There's lots of good general info here too, from another show breeder:
http://roycroftcavaliers.com/manualfeeding.htm
The relevant bit on puppies:
FEEDING DIRECTIONS
Whether you decide to feed a high quality kibble or a commercially prepared whole foods diet, the following directions will apply.
Puppies between 8 and 16 weeks of age do quite well on 3 meals a day. They start out with about a large handful of kibble for each meal or about 1/4 cup. At about 4 to 6 months of age you may begin feeding your puppy twice a day, about 1/2 cup or so each time. Somewhere between 10 and 18 months of age you may begin feeding just once a day--with some really good eaters you may need to feed just once a day by 6 or 7 months of age.
Each time you feed your puppy, put the food down for approximately 15 minutes. If the puppy hasn't finished it after 15 minutes, pick it up and put it away until the next feeding time. Do NOT try to feed in between. Refrigerate if you are feeding a commercially prepared whole foods diet. Do not worry if your puppy appears thin. Puppies are just like humans. Some are very thin while growing up and some are not. It is highly unlikely your puppy will starve itself unless it is already ill. A puppy that grows slowly is best--there is no first prize for gaining full size as early as possible! Puppies who grow slowly are more likely to be able to develop muscle and tissue at the correct rate to keep up the the bone development. Of course some puppies are gluttons! Be careful not to overfeed a glutton.
Many breeders feel you don't need to feed puppy food; I never did. Also as Cathryn notes, I wouldn't be softening food at this point and would be giving some dried. I'd drop the weetabix and bread, and select a good quality food -- Pedigree isn't the best and has a lot of filler. I recommend James Wellbeloved, Burns or Royal Canin small breed, of the quality foods that are easily available in Ireland. I get the large bags as these cost up to a whopping 50% less per kg than buying the tiny bags. I would still add an egg a couple times a week and would drop the milk as your puppy is getting around the stage where they can't digest lactose any more and you are likely just to cause gastric problems and the runs with too much milk (same for cats!). The meat is a good and tasty addition too.
I feel you can easily feed puppies a variety of foods -- after all they are omnivores. If you feed one thing all the time, they can get to be very fussy eaters about only eating that one thing. I always like to add something to kibble but use kibble as a base for meals to keep things well balanced nutritionally.
As Cathryn notes you will find he will soon start to ignore one of the meals, most likely the midday meal, and at that point discontinue it. Most puppies will not overeat but it is important not to free feed them for a variety of reasons -- harder to track what they are eating, for one, and also that encourages a glutton as they reach adulthood.
I also feed just once daily, in the morning, but some like to feed twice. The main problem with feeding twice is they get such small amounts then in each meal that people tend to overfeed to fill up the bowl a bit more. This is on reason I recommend using small cat dishes for feeding; it's way too easy to give too much food in a bowl that is too arge for the breed!