Is my kitchen design OK ?

There is an island in the same room, in the middle of the floor with a sink (not shown).
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Why do you have 2 sinks? Get rid of the sink on this plan and you will have much needed worktop space as there isn't enough (in my opinon) in the current plan.
 
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Does it have any design flaws ?...
As per other posters, lots of flaws IMHO.

Is that a larder door on the extreme right?

Do you have a plan view you can link to showing the island and other units?
... someone at a well known retailer design me a kitchen for a new house...
At a guess their full-time job isn't designing, building or working in kitchens (or shouldn't be).
 
I'd try for lots more counter space - very small area here between the making up of food and then the plating up, there doesn't seem to be much room at all. Need more space at side of hob too - you need to be able to put down hot saucepans/roasting tray in a hurry sometimes. Do Belfast sinks have draining boards? Definitely need a draining board whether for rinsed out dishes or for washing veg/etc.