I had everything [like my bank accounts] down as being:
[room number] [block]
Post does get to you if you just put your college and name down though but I have a really common surname so wanted to be extra clear with my mail. The different colleges have different postcodes so either use the general one for Lancaster campus [LA1 4YW] or try to find out the one for Lonsdale.
Yeah you don't have to put your room or block number, just the address of your College should do, then the Porters will filter the mail out alphabetically into your mail boxes, regardless of whether your room/block number is stated or not. Your address should be the same as Cartmel's, where I'm from, apart from the College bit of course :P