Please could somebody tell me what size trousers I should be buying for a boy with a 23" waist?

[TooTicky]

Ds1 (7) keeps growing out of his trousers, especially the school ones. 7 is too small, some 8s are too small and some are too big, the same with 9s. But he doesn't have very long legs and likes to wear his trousers low. Help please!

tescos do adjustable waist trousers so you only need to worry about the length

Now that's a sensible idea