Well true, but the end result is the same. First two (IKEA & Homebase) are flatpack. The local shop & second hand are pre-assembled (the second hand is real wood construction so was never flat pack), but it makes little difference.

Self build, sure, there is a labour "cost" - but you're looking at a couple of weekends max construction, so if you have the interest it's no biggie :) I only included it because I thought it would be interesting to encourage people to consider it as an option.