The PGDL takes one academic year, so, yes, about nine or ten months.
A science degree plus a PGDL would be a good basis for practising patent law. Mr Justice Mellor, the Patents Judge, has a degree in Engineering from Cambridge. Patent Attorneys (a sub set of IP lawyers) have to have science degrees. My friend who is a Patent Attorney read Physics.
A law degree can give the young lawyer some initial advantages because he or she may have a more thorough grounding in the law than a non-law graduate. After a few years in practice, however, a non-law graduate should know as much as a law graduate. I read History, and then did a GDL. I've been a barrister for a zillion years, and have even taught law at universities. About half of the lawyers in the UK have a non-law degree.
Do a degree in your favourite subject. Have fun!