You can have your doctor sign it for you, even if they haven't known you for two years. Other professions who can sign;
a local business person or shopkeeper
a librarian
a professionally qualified person, for example, a lawyer, teacher or engineer;
a police officer
a bank or building society officer
a civil servant
a minister of religion
a magistrate and
A local councillor or an MP (AM, MEP and MSP).
It's £38, and upgrading to a full license is free. Except of course for the cost of testing.
Most of that information should be on your forms though. The theory test is £20.50 and the practical is £39 for weekdays and £48 evenings and weekends. Look for more information at the driving standards agency website.
Your license will be good until you are 70, though you have to renew it every decade or so - this doesn't require resitting a test or anything. After you are 70 you will have to renew every 3 years.
Rosie