This is a great way of utilising space in the attic and adding tens of thousands to the value of the property, however you may require the services of an Architect and you will require building regulations, as it is a legal requirement. If at a later date you may wish to sell your property, the sale could seriously be affected without building regulations and you may find that you have a few difficult obstacles to negotiate. Make sure you consult with the council and get advise whether it can be achieved.
Below is an example of a loft conversion that was done in Llawhaden.