In the kitchen retail industry, Wren is universally considered to be the epitome of awful both to work for and buy from.
If there's a devious and consumer-unfriendly practice, they do it.
Their product is wildly overpriced for it's spec and they rely on the glamour of their showrooms and "time limited special deals" to wow and pressure customers into signing up with them.
Wickes is by far the better option; you'll still pay considerably more than you need to if you go for the full package (Supply & Fit + Finance) but their designers are far better and their product & installation is good.
Magnet's not awful, but again you'll pay over the odds for the spec.
B&Q is not a great choice for home users, imo. Their product is cheaply made, very limited in style/design and decidedly aimed towards rental or resale.
They're basically Howdens but flatpack, a bit cheaper and with far less options.
If you're looking for good value but at a reasonable price, visit an independent and get a supply only cash price, then engage your own fitter. You could save a fortune and end up with a superior product.