nana2006
The cost. Well a lot depends on where you live. Your talking about a new roof, what tiles do you want, it makes a difference to the cost.
Do you want a bathroom in the conversion ( I would think so)
All I will say is: be very clear as to what you want as any change of mind on your part could be costly.
Have people in your road had a conversion? Were they happy with it? ask them. There are a lot of cowboys out there, be careful.
Also, don't look on Check A Trade. Every trader on that website has to pay to advertise his work, no good tradesman has to advertise.
My ex son in law specialises in loft conversions and is renowned for his work. You will never see his name advertised.