Hi Ctrain,
I haven't been on long-haul flights, only within Europe but the restrictions for hold-luggage as far as I am aware are only to prevent risk to the flight (i.e. explosive or flammable components etc). Again, this is only in as much as I am aware, but there wouldn't be any problems in taking kitchen knives from one country to another so the same rule should apply to pocket knives (although the former should be in a locked case, I think your suitcase is enough).
I am sure you are aware of the law concerning carrying knives in the UK, from memory it is based around s.139 CJA 1988; for the 'pocket knife' exemption the blade must be folding (stipulated as non-locking by case law) with a blade length of less than three inches (76.2mm), further case law has indicated that this length relates to the sharpened edge and is not integrated in the case of serrated edges. You are not allowed to carry a pocket knife on school premises (s.139A) and if the knife is used in a manner which is considered to be
"any article made or adapted for use to causing injury to the person, or intended by the person having it with him for such use" (i.e. offensive or defensive use) you will find yourself in very deep water.
I know you didn't ask about the knife law in the UK but I have added it for reference in case it is of any use, another reference is the Criminal Prosecution Service website
http://www.cps.gov.uk/legal/section12/chapter_c.html.
I hope you enjoy the UK.
Andrew