For my son (tiny butt, tiny hips) any bottoms that didn't have an adjustable or drawstring waist i had to take them in with a needle and thread. Leggings would have just fallen down on him after he stopped wearing nappies at 2.My son has skinny legs and we can't get leggings for him as they don't have adjustable waists so fall down to fit his legs. So her comment that skinny trousers don't fit but leggings do is nonsense. The only way leggings are staying up if he does have skinny legs is a nappy is holding them up
Also her saying that the tescos baby range wasn't in his size means he isn't tiny at all as I just realised when I washed a jumper for my son this morning that it was 18 to 24 months from tescos and its still big on him whereas he is in 3 to 4 at primark.
I also found that Tesco clothes (F&F) ran larger as well. His clothes lasted for AGES because he took a long time to grow into them. I certainly didn't need to keep going out and buying him new stuff because everything was too small.