The layout of your new kitchen will depend on a number of factors, not least where the waste water from your sink, dishwasher and any other appliance that uses water, enters the drainage system. Moving any of these is not normally a problem but you may be restricted as to where certain appliances need to be positioned in the kitchen because of where the drains are. The usual method of planning a kitchen is to design the layout making sure you keep the distance between the key elements to a minimum. Having the food preparation area close to the sink, cooker and fridge will ensure you don't wear yourself out, running from one side of the room to the other. Without seeing the size and current layout of your kitchen, it is impossible to make any further, useful, suggestions. Choose your kitchen fitting company vary carefully and don't be shy in asking lots of questions, if they are any good, they should answer all your questions in detail. Hope this helps.

To answer the basic question, no, there is no particular requirement to have a sink at a window, though many customers like this for the reasons stated. Given the layout of your room with the full height windows?/patio doors, it would not be a practical suggestion. On first looking at the Wren design, my thought were much the same as OnePlan's - there just isn't enough workspace and I can't see any particular dimensional constraints to have caused the design to end up this way. I much prefer the second design, and see no reason why this couldn't be achieved in your kitchen - incorporating seating as OP mentions. Wrt underfloor heating, this would normally be laid around the island/peninsula and not under it or the other units, so no great issue. Planning a cable route to the island/peninsula is also straightforward - just make sure it is properly planned for the first fix. Wrt plug sockets - pop up would, I feel, be more attractive than a standard socket under the worktop, though they achieve the same. And if you want a bit of "wow" factor for a very reasonable cost, check out the "S-box" pop up sockets/spice racks/knife blocks to really liven up an island! Wrt Wren - make sure you have a good handle on the total costs of all aspects of a kitchen installation, as they do not always declare all of these to you until you are committed and deposits paid. After conversations with other customers, I'd also urge you to carefully read online reviews (for example Trustpilot) to be sure you are happy with their ongoing customer service.

Where is your bin going to be? I end up doing veg prep near the bin as it’s so much easier to put peelings etc in there. I’m guessing your bin will be near your sink and dishwasher, so suspect that area will end up being your prep area even if you put a sink on the island. My parents have a small sink on their island and almost never use it for this reason. If you want to do food prep at the island I would suggest considering moving your main sink and bin there, rather than having an extra small sink. You have a raised breakfast bar so that would hide any sink mess (also if you get a large sink you can put dirty pans in it which helps hide mess while you are eating). Having said that if you use a food waste caddy, that is moveable and you could do veg prep at the island if you had a small sink.

I would go with a white porcelain or ceramic sink. No need to worry about seeing hard water spots with them. And you can add some contrast to the monochrome scheme by using brass / gold taps. We had to skip our intended quartz worktops because of timing issues (long story involving family visits and lockdown), but nearly 2 years on we have been very happy with our Duropal 20mm Carrera laminate worktops. I don’t expect them to last “forever” like I might for quartz or granite, but its also nice to not cook in fear of potentially damaging a very expensive investment either.