Here is my lovely little kitchen (photo taken back in October - excuse the washing up).
As a rule, houses in the UK are generally pretty small, and way way smaller than American houses. As such, rooms are smaller too! I think my kitchen is actually a pretty reasonable size (2.8 x 3.9m) and I love that I'm able to have a four seater kitchen table too.
One of the main differences would be that we have our washing machine/dryer in the kitchen (although I don't own a tumble dryer - the previous owners of the house had one in the garage though), unless you are lucky enough to have a utility room, which would be situated off the kitchen (my parents have this in their house, but it would be ridiculous in my tiny two bedroom place). Mine is under the sink.
I don't have any issues having the washing machine in the kitchen. Some of the comments on the forum discussion mentioned about clothes smelling like food, but I don't actually dry clothes in the kitchen! If the weather's nice everything goes out on the line in the garden, and if it's not it goes on the airer, which I have upstairs in the spare bedroom (out of the way). Not having a dryer doesn't bother me at all ... I have always been able to get everything dry without smelling musty no matter the time of year, and it saves money on bills. Saying that, if I had a large family or a baby I think it would be a different story.
The kitchen sink. One thing that massively confused me is that most American sinks have no draining board/rack. I do not have a dishwasher, so all of my washing up is done by hand (oh the joys), so a draining board is pretty much essential. Also: no garbage disposal!!! Those things freak me out and luckily no one has one over here. I'm pretty careful with what food I buy so I hardly ever throw any food away (I save leftovers or force myself to eat everything no matter how uncomfortable I feel - money is precious!!), but if I do it goes in the bin, or out for the birds, or in my makeshift compost heap (spring goal: buy a real compost bin).
Gas boiler: located in a fake cupboard in the corner of the kitchen. This is pretty standard, unless you have the aforementioned and much lusted-after utility room. The fake cupboard means you don't know it's there, but it also takes up space.
Electric kettle. Obviously essential in any British home. And I'm pretty sure there is a law that says you must constantly be making tea. If there isn't there should be. I totally did not even realise that Americans rarely have an electric kettle (I guess it's more fancy coffee machines?). This was probably the first thing I bought for this kitchen.
Built in cooker/hob. Someone on the forum said that built ins were more expensive than free standing... I guess this is slightly true over here (?) but I have never lived in a house with a free standing oven, even as a student, and I don't exactly live in an upmarket area (think: deprived). I think they look so much nicer this way, and see the panel underneath? Secret storage for trays!!
I'm sure there are loads of other differences (another one I thought of is that we don't have built in microwaves), but these are the main ones that feature in my kitchen! Can you think of any others?