A question to all you Brits...

Any of you think you can explain Bristol University's system to me?

Like, what are teaching blocks? Are blocks 1-12 fall semester while 13-24 are spring, or are both fall (Fall semester=September-January)? How many credits does one typically take at an English university? How does a 6-week course relate to semester-long courses? What on earth are all these "levels"?

Any help for the poor confused American would be very very appreciated!

(Also, Bristol or Royal Halloway for a semester abraod... Any opinions?)