I've installed IKEA wardrobes, dining room cabinets, and a B&Q kitchen.
My advice, for what it's worth....
To get it right, and look good, there is a LOT of planning. It makes me appreciate the amount of work kitchen installers do. Every kitchen is different and getting all the various units, countertops, kicker boards etc. to fit is a task in itself. That is why there are dedicated staff in B&Q who's job it is to sit down with you and plan your kitchen.
I enjoy the process, but if you don't, be aware that it will get frustrating, and can't be avoided. It is a lot easier with an expert sitting with you. I don't know if IKEA provide this service, but the likes of B&Q etc. do.
Also with the IKEA units, because they have to be built to accommodate all types of walls (block, stud, etc.) then they come with a raft of fittings and adjustments. Similar with all door hinges. They are all adjustable in 3 dimensions, and used correctly, make the difference between the finished product looking good and looking thrown together.
And while all types of fittings are standard enough, there are differences between manufacturers/suppliers (C&C, B&Q, IKEA). So, someone who is familiar with IKEA assembly will do a faster job (and probably better) than someone who is not.
Quality wise, they are fine. The IKEA units don't get much rough wear, and hold up fine. I don't know about a kitchen. I doubt they would last as well as higher end kitchens e.g. Remp, but then you are getting what you pay for. Maybe you're the sort of person who wants to change your kitchen every 5 years, or who lives alone and will be easy on a kitchen.
The B&Q units are similar, I have it installed in the utility room and they are holding up OK. Same quality caveat applies as the IKEA.
I'd suggest, as Sue Ellen does, going to B&Q, Cash & Carry, and The Panelling Centre with your kitchen dimensions. See if you like the styles they have and sit down to see what they will design for you. Then look at the overall cost for supply and fitting, by their recommended installer.
The other advantage of using a recommended installer is that they should take more time in satisfying your requirements as they have a closer connection with the kitchen supplier, and you have better comeback if anything goes wrong. If you use your own supplier and the cooker hood breaks down, or a door falls off its hinges, the supplier can claim it was the fitter who caused the issue.