I’ve used DIYK in the past and been happy with them, but, also wanted to flag. I’m doing work to our house so looking to buy again and - I’m starting to see the same reviews, using the same wording on several ‘pro’ diyk sites at the moment (here and Facebook). I suspect their marketing team do a great job.
The advantages of DIYk: clear pricing structure, high end quality products, relatively easy install (cabinets are premade but be aware the void spaces are smaller than some other high street brands so when planning this may need to be considered - it was a plus for us in a slightly smaller kitchen space!).
Cons - delivery process is tricky (and seems to have gotten harder from others reviews) with limited notice and notification, if items are damaged (esp in transit) or need replacing the process is fairly time consuming and involves waiting for redelivery. Self design (though they’ll match other high street places plans).
For ours, price wise when pricing at the moment they compare to the likes of howdens (solid wood ranges). Personally, id have loved to have been able to finish our build with the kitchen Magnet designed (preferred style) but can’t justify the DIYk difference.
BUT the buying process has been much more frustrating than previously : eg. Have paid for several sample doors that are not delivered (sent colour swatches instead but tiny pieces not helpful in choosing a range or seeing quality). Presuming as they grow, demand is putting them under pressure. But my advice would be that using DIYK takes a lot more time than other suppliers - for all parts of the process (design, getting samples, ordering - basket can take a few days to be checked, turnaround on bespoke paint can be longish, checking - advice is at minimum two weeks delivery before fitting so you need storage etc.)