Yeah, there should be some way of accessing the information of any invoices for works done, MOT history, Service History, just a paper trail of everything other than fuel that's gone into the car IMO. I'm going to ask the salesman on Friday, however, when I had a read through the documents when I was searching for the timing belt history, there was a good chunk of paperwork, which is good, I guess!
lets face it, you ultimately buy a 2nd hand car based on 3 things - Cost, How it drives and History!
I have found in the past, like you said, warranty isn't worth the ink its written in, hence why I didn't pay extra, but I do have that as a first port of call if something goes pete tong.