Agree with the others that you need to replace the window first before you go any further, otherwise you will always have problems. The shower is also very large for the small room. Is there any way that you could re-configure the room to have an enclosed shower on the wall opposite the loo? With the boxed in pipes, you may find if you dismantle it - the box does not need to be so large. If you do not want tiles (which personally I hate because of the grouting) - how about wall boards. These go from floor to ceiling, can be cut to size, and no grouting. Presumably you open the window for ventilation - so a fan is not needed.

Switching the sink and loo seems a good idea to give you a fantastic vanity area with storage above to reduce the clutter. Since your entrance door is angled it won’t be the first thing seen on entry. Your idea of removing the air vent from the window - what is the plan for it’s replacement? It’s doing an important job of dehumidifying the room and a replacement will be required to maintain the pristine ceiling and grout! We recently refurbished a downstairs loo - lots of fantastic independent bathroom showrooms here in Hertfordshire. We had amazing ideas suggested to us ( some with amazing prices). We used the concepts from the very expensive design ideas with slightly less pricey option. We would not have thought of these ideas without the help of the experts, and they identified snags in our initial design that would affect the surface lines and finish that we didn’t know existed!

We built an extension a few years ago with a similar kitchen to option one, including a peninsula. The layout works well and I’m really pleased with the functionality of the design. We have a cupboard either end on the lounge side of the island and stools sit in the middle, plus a dining table close by. I agree with all the comments above about stools, they are used regularly. One thing I would change is our light switches are the on the lounge side of the peninsular and that means walking round to put a light on when working in the kitchen. Ideally, it would be best to have the switch on the kitchen side. We have pendant light over the island, which looks good and again are functional. Final, thing to say is it’s worth every penny! Open plan living, extra space, lots of light from roof lantern and bifold doors into garden are all brilliant. 4 years on I still love it and appreciate it every day.

Brett, I have worked designing kitchens and bathrooms for over 30years. You have the wrong system, you should have a standard boiler with in unvented hot water tank this would give you great pressure all over the house. Water pressure is measured if feet of head which in days of old was the difference in height of the top of the shower and the top of the cold water tank so in a 3rd floor this would be 2 foot to the ceiling and 2 foot in the attic, with an unvented system you wold have about 112 feet of head.