The best word of warning is quite simple Don't change your mind!
Once you have decided on your design and actually began the project it is often impossible or impractical to revise your scheme.
Quite often people get in to a project and then change their mind and think they want to do it a different way. The obvious problem with this is that it will probably cost more money to start over or change directions.
While converting the loft can add value to your home you don't want that added value eaten up in the cost. Indecisiveness is usually the biggest reason that some people won't even attempt a loft conversion.
Have you got this kind of roof space? If so you've cracked it. Your loft is absolutely ideal for conversion into basically any design you like.
This type of roof is exactly right for a loft conversion as it has a steep pitch and lots of clear space between the timber framework.
As a very general rule of thumb the older the house the more roof space you are likely to have as in the past the tendency was to build houses with a much steeper pitched roof than is normal today.