I bought a cheap unofficial Lennon DVD the other day entitled In My Life. I didn't really expect much as it cost me 1.50GBP brand new but it isn't that bad.
The only thing I didn't like is that it focusses heavily on his death and the days after... news reports and interviews with certain people about where they were at the time, etc. There's also a short interview with Mark Chapman but I have forgotten what he talked about... probably the usual crap he drones on with.
Anyway, if you find it to be as cheap as I did, buy it, but I wouldn't spend over 5.00GBP really, unless you're a die-hard!