I was in a similar position to you end of last year. Bought a house that needed a new kitchen so I was shopping around.
B&Q - Horrible kitchens, at least in my local stores. Everything feels really cheap, the designs aren't all that great and the prices weren't very impressive either. Might be fine if you want to stick a cheap kitchen in a property to sell/rent but I couldn't live with it long term.
Homebase - Marginally better than B&Q, some better designs and sligtly better feel to it, but generally of similar quality.
Wickes - My favourite of the DIY chains, their top range kitchens can match Magnet and Howdens on price but they do a few decent ranges in their budget kitchens. I expect the units are the same and just the doors are different. Would probably have spoken to a designer if they ever had any in the offices in the stores.
Magnet - The guy came out to the house to measure up. Was keen to make sure we would be offered the current/recent discount off RRP. Didn't really follow instructions very well with my requirements so it meant when I met him at the offices he had to redesign the kitchen.
Ended up being fairly reasonable but I didn't like the design and finish as much as others and their worktops were expensive. They could offer free cooker appliances though.
IKEA - I really liked their Kitchen design software. Meant I could play around with things myself and see how things looked and worked together. Liked some of their units too, although the finishing isn't great but it allows for a lot of customisation, I also liked that their prices are transparent so you can easily see exactly what costs what without having to factor in discounts and things.
However I was warned that the units and standard and a big point was they don't have a gap at the back of the unit for any pipework/cabling so it either has to be inside or underneath.
This can cause extra work for the fitters if they need to re-route things. Also I wasn't too keen that it is down to you to make sure the design will be appropriate. You have to put down a deposit before a surveyor will come to your porperty to measure up, at which point you're down around £100. They do.did offer some nice insentives though, like spend £1000 on a kitchen, get £100 voucher.
Their ovens are tiiiiny though! Their sinks are also rather poor - with tiny draining boards. I do have their pull-out extractor fan though. So I'd consider getting different appliances if you go for IKEA.
Howdens - This is who we ended up going with in the end. They were friendly gave good help, after speaking to them on the phone and arranging an appointment to visit they dropped off a brochure so I could look at the styles and units before meeting. The designer came up with two designs that were good, although I had some more tweaks to my final design to make better use of the space.
Unfortunately their design didn't work out quite right and I ended up with a drawer that couldn't be opened due to the oven handle. Also I had requested two bins to be put in the sink unit however once the popework was done there was no way these would fit. They were also rather poor with their deliveries, not calling in advance when they said they would and not delivering everything at the same time.
They remedied the drawer problem by having to remove the drawer and fit new doors, but I still have two bins that I can't use.
Other than that I was very happy with the finished kitchen, we had our own local fitter who had worked with them before and it has been good to use.
I bought wall and floor tiles separate and they were fitted by someone else after the kitchen was complete. With all the units coming assembled you need a lot of room to store it before you start fitting. It ended up filling my living room.
Also be aware that the worktops only come at certain set lengths. I have quite a lot left over after it was cut.
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I was fortunate that they were pushing for end of year targets and got quite a few things in their 'deal'; free worktops, free oven, 50-80% discount on most things. I'm sure that there are deals to be had all year round though and they seem pretty open to 'tweaking' the price if you just ask.
Good luck getting it all sorted. I actually quite miss the designing and planning of it but now I'm enjoying cooking and using it.
