And one similarity between the US and UK systems is first past the post elections, which you initially claimed was a difference.
One major difference between the the US and UK systems is that in the UK the party directly chooses who will run in which districts, giving the safest districts to higher up leaders and loyal party members. This leads to more loyalty to the party platform in parliament (fewer cross-over votes, I imagine, than in the US Congress), and as a result in the UK you are usually voting for the party, whereas in the US people are often voting for the personality.
Funny, though -- maybe some of our British comrades should be commenting on this.