If you want to understand how the UK Intellectual Property (i.e. Patent) Office exams patent applications relating to “software”*, a good place to start is the most recent Practice Notice:
Patents Act 1977: Patentability of computer programs (Recent= 8 December 2008).
The most recent Practice Notice builds on a previous Notice:
Patents Act 1977: Patentable subject matter (dated 2 November 2006).
This previous Notice was also updated by short Notice:
* By referring to software in inverted commas I am indicating that the term “software” patent is not often used within the profession, which prefers the terms “computer programs” or “computer-implemented inventions”.
With regard to protecting computer games at the UK IPO see the Practice Notice:
Patents Act 1977: Patentability of games (updated 2 November 2006).
Basically, games are not patentable. Paragraph 4 of the Notice is superseded by the Practice Notices above.