4. There is no such thing as "we don't have a budget".
Rather than setting a fixed figure like £2000, better to set a range. Be clear with yourself what your range is. What is it that you expect from your range? If you're looking for a large "L shaped" top grain Italian sofa with recliner, storage, sofa bed and a jetpack, will your range realistically cover it? Make sure you set a realistic range before and during your online research.
5. Take lots of photos / videos.
Take lots of photos of the room where the sofa will be placed. Take a video too. Don't just take photos of the wall or corner where the sofa will go - be sure to get a complete 360 of the room.