No competition at all. None whatsoever. The only friction between development teams ever at Psygnosis was when an "ATG" (Advanced Technology Group) was formed to "research" new technology. The joke was that ATG stood for "another ten grand", and nothing ever really came out of the group at all. They lived in a room with a numeric keypad on the door. It was where the first Playstation (although it was still called the PSX at that point) went when it arrived - bigger than an office photocopier it was, with a massive row of fans all around the bottom.
Martyn Chudley (who became Bizarre Creations) and Traveller's Tales always had little jibing in-jokes at each other in their games. In Wiz'n'Liz, for example, there is a sub-game where you throw tomatoes at Andy Ingram and Jon Burton from Traveller's Tales, and in Puggsy you get to pick up a laser and shoot rabbits that look remarkably similar to the ones you have to pick up in Wiz'n'Liz. It was all in good humour though.
Commodore UK was pretty good, but don't forget that Shadow Of The Beast was what made the Amiga stand out from the crowd so we were seen as being pretty important. We got prototype machines and stuff. I never really heard anything bad about Commodore UK; they did a pretty good job I think, but it's possible that other developers may have a different view. They were still profitable when Commodore died and if you remember they attempted to buy out the company from the liquidators. It's possible the Amiga would have taken a very different path had they succeeded. Commodore in general, as we all know though, was awful.
After the death of Commodore, David Pleasance of Commodore UK went a produced a CD called "Everybody's Girlfriend" using all Amiga gear. I have the one that he sent to Ian Hetherington, our Managing Director. He plays a a pretty damn good spanish guitar!