Blitz, as a company, never had anything published by Codemasters. However, Andrew & Phillip started their careers developing the Dizzy Games for Codemasters, the IP of which is still in joint ownership. This was the only collaberation between the two companies, although there was several attempts at ressurecting Dizzy in recent years.
TruSim is a pretty interesting development – they have completed one project to my knowledge, to be used for teaching surgical techniques, and had a couple of other projects in pre-dev when i left last summer. It’s pretty good to see games branching out into furhter areas than purely for entertainment i have to say.