Without wishing to appear to be giving an evasive or unhelpful answer....
Depends on how you define "best value for money".....hopefully this means providing the most acceptable nutrition relative to your pockets.
Dry extruded kibbles worth considering compared to your current feed.
Can be cheaper per kg without significant compromise maybe look at Autarky, ,Skinners F&T, Chapel Farm 24, Arden Grange, (have fed all of last 3 before I decided to go grain free).
Spending a bit more look at grain fee choices from Wainwrights, Simpsons, Eden Millies Wolfheart, (fed a couple of varieties of this brand).
Higher price consider Acana, Orijen which are imported to uk with considerable UK retail cost. Fish 4 dogs & Akela worth a look perhaps (fed the later prior to changing to decent raw complete).
I currently feed decent quality raw complete minced products, mostly but not exclusively Wolftucker & Nutriment brands. Raw feeding not for everyone & for various reasons. My current choice made for a variety of reasons, (including keeping simple carb levels low with aim to supporting a prior diagnosed condition).
If open minded, wanting fresher food than some dry extruded products (but not wanting to feed raw), then perhaps look into decent quality cold pressed foods......this is an area of the dog food market which is growing in popularity. Quality can vary so do look into this properly. Gentle & Guru are just two cold pressed brands favoured by some on here.
The forums have various threads discussing specific brands &/or food types. Plenty of other brands out there which I have not mentioned & that score similarly to those I have named.....so maybe look at other brands too.
Many chose specific food types or brands with little thought or on back of poor recommendations from friends &/or family. The wiser owner does some research & importantly considers all factors, not least including the needs of the individual dog(s)
Take a look around, read posts, reviews & do your homework before deciding what if any food types &/or brands you might want to try. The guide allows you to compare approximate daily feed costs ratings & composition.