Personally I'm not a massive fan of JWB because of their "special added ingredients" and since their factories were taken over a few years back the food hasn't been such high quality.
That said, it's not a bad food, it's good in fact but I think there are better foods for less than or equal to the price you pay for JWB.

The important thing which a decent food is that a specific meat (e.g. chicken not "meat and animal derivatives") should be the first ingredient.
Ideally you'd also look for something wheat/gluten free, as my understanding is that wheat and simular grains don't actually have much nutitional value to dogs anyway and are difficult for them to digest.
The following link tells you what to look for in a good kibble:

Choosing a good kibble (dry dog food)

Here are a few foods that I think are good quality and value:

Orijen
- 75% meat and 25% fruit and veg.
ORIJEN Biologically Appropriate Dog and Cat Foods | Orijen Pet Foods .co.uk

You can buy this at Zooplus as far as I'm aware

Applaws Dry dog food
- 75% meat

MPM Products - Applaws Natural Dry food

- They also do a wet food

Whites Premium

Whites Premium Puppy Dog Food Analysis

Burns

Burns Pet Nutrition - Real Food For Pets

Arden Grange

Puppy Food from Arden Grange

CSJ
CP27 Puppy
CP27 (Puppy) - CSJ Command Performance - CSJK9 Ltd.

CSJ-Original Natural Puppy
Natural Puppy - CSJ Original Dog Food - CSJK9 Ltd.

Skinners

Skinners Puppy and Junior
Skinners Dog Food | Puppy & Junior

Then wet foods:

Naturediet

-60% meat- high palatable- excellent totally natural food (nothing artificial at all! )
Natural Dog Food | Naturediet

Like you said your pup is doing fine atm on the JWB, so if you are happy with it, then the old phrase "If it ain't broke..." could well be relevant.

However whilst JWB is still a good food, IMO there are better foods on the market many of which are more economical.

Hope this helps anyway

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