To follow on from some useful posts here: BTU calculation is absolutely your starting point. Better to oversize the rad rather than undersize, especially if you are using a modern condensing boiler that runs at lower temps for greater efficiency. So make sure that the BTU output quoted for the rad is at the temp you will have the boiler set to. A Pro like FR above can give you this info. We used Revive Radiators' steel column rads throughout the house. Being steel, as opposed to cast, they can be tall, and come in a 1500 size, 1200 size as well as the standard 1800mm. We actually have them in 2000 in the pic below. Ordered from mrcentralheating.co.uk who are helpful and reliable (i've used them in all three of my renovations). The rads have been fitted in my flat for over 10 years now and perform perfectly, so they have been tested. I'd definitely go with one tall rad, as it will free up floor/wall space for other stuff, like a feature chair or table, plants on the floor during the summer etc. Not a great pic, but you can see a 2metre tall, 3 column variant in lacquered raw steel finish on the wall of our new house next to the living room door. Behind, in the hallway, is a white, horizontal variant. The ugly plastic device on the valves are Honeywell's Evohome TRV controllers, which I cannot recommend highly enough (apart from the plasticky design), for temp control for each room individually.

@rinked Thanks, good idea - i'll see what it looks like later. @Suzanne C thank you for sharing your experience and pictures. We'll be going out for quotations once our planning is granted so i'll make sure i get a cost for wet UFH. I think it would be the preferred route with the warmth underfloor and extra wall space is always good in open plan extensions. @minipie Thank you. The software really is great once you get to grips with it. We've started to obtain budget costs on the roof lights and one company has offered to take us to see a few recently completed projects which should hopefully give us some inspiration and allow us to gain some feedback from previous clients. I'll aim to get at least one opening roof light after all the advice received on this board. Thank you for sharing your experience. I'll look into the small radiator in the bathroom. Good idea. The extract routes are pretty easy as the kitchen hood is on an external wall, as is the utility. The WC fan will follow the existing route above the utility rooms ceiling. Not sure on the subfloor as not taken up any flooring so far but the house was built around 2003 so you'd expect a pretty thick solid concrete slab so it might not be as easy as excavating in an older property.

Hi, Thank you for the photos, now I have a better understanding of the whole area. Yes, the sofa looks better after turning it around, but if you`re planning to buy a new one (or loveseats), it would be better to think about some modular sofas. They are easy to move in a space and you can match different sizes and colours as well. What do you mean with the option “c) separate the nook area with 3 white wood panels hanging from the beam”? Sorry, but it was clear to me. Regarding the TV nook I was thinking about the option to leave the TV and the cabinet where they are and use the walkthrough path between the column and the half wall as a storage place (see photo). You can place there a shelving system, which can be used from the dining area as well. You mentioned that you don`t like bumping into the sofa after entering the room. What about to create a small hallway and use some room dividers to make it cosy entrance, where you can sit down to take off your shoes and leave the keys and bags on a side table? The room divider should be something massive (wood or metal), but also something transparent to avoid creating dark corners. The playing nook can be placed in the corner next to the seating area (adding extra lounge chair optionally) and the home office on the other side of the dining area . Now I hope that you have enough inspirations and options to think about. Good luck and enjoy your new layout! Regards, Mariann

What a lovely room. However that picture rail is really low. I have a similar room in my 1930s house and the picture rail is higher but then mine doesn’t have the big ceiling. I’m thinking if you want to paint the walls then paint it all, up to the ceiling coving and leave the ceiling white (I love a white ceiling). Do you have favourite colours? I love blues and greens but you may not. How do you feel about a deeper colour like F&B Oval Room Blue, or a green like Pigeon or Green Smoke? Or a lovely pale yellow like Hay. So many choices! Below is my sitting room (pale green) and the next picture shows where someone has painted one colour right up to the ceiling.