Hi again Jane. Any external changes, including windows, may require planning permission. If the property is a block of flats or mansion block this may be more of a challenge. You may have permitted development rights, which can be another good option. Any change, however small, is likely to be subject to a license to alter especially if there's a management company or a remote freeholder. This includes windows in any shape or form. As unreasonable as it may appear, The licensee / freeholder can quite legitimately sell you the space and the roof structure and then request a full license to alter application. It's also not a given that the you be awarded the license. Sorry if this comes across all doom and gloom. There usually ways design challenges. understanding all the risks as well as the potential is important.

Hi - just letting you know that I've replied in [the other thread[(https://www.houzz.co.uk/discussions/front-of-house-dsvw-vd~4585018) in case you don't see it!

If you decide to proceed make sure the loft has been built to building regs (This is a solicitor job). Because the stairs don’t sound like they meet regs it could be the case that the owners of this house have in fact not strengthened and insulated the loft which are expensive jobs. If you don’t have the building regs then it is not a proper room and you shouldn’t be paying for it.

Firstly Congratulations on your first home, well done! got to say I don’t really understand why there are two radiators in that room as big one will be enough I think…small room. put small folding extending dining table and chairs at bottom of stairs by window tucked away. Extra chairs can live in the cupboard and then extend table if you need too in the room. TV and computer desk could become a multi purpose unit…think bookcase with arm for extendable TV and computer in same place? Or knock out under the stairs as complete wasted space now and put your desk etc under there. TV on wall with a multi positional arm saves floor space. Can see TV from wherever you sit/eat then if you can afford it and don't really need a computer then get an ipad. Go on Pintrest for ideas and look at Ikea layouts , they have small spaces and make it work. Sofas are up to taste but keep a tape measure with you always… Lots of luck