I'm not sure if you're setting expectations with him. I have this problem to some extent. Some of our guys email around everyone telling them what they're doing, asking questions, trying to get feedback from everyone else. Others have clammed up, don't talk, shut themselves in. When the guys that talk about what they're doing (and some of it is weird obscure stuff, so they kindly abstract it) then you know they've been working hard. The guys who were quiet, never said anything, then you walk past them one time while they're taking their lunch late at around 3 because they've been working on something, well it looks like they've been goofing off. The reason is that this is all the information that I as a manager have been provided with. I know my guys enough to know that they're not goofing off, but it can be a bit like herding cats sometimes.

If you tell your boss what you're doing at a high enough level ("I'm working through this set of problems to do with the way the car valuation service talks to us - they don't have any documentation so I'm having to work it out by hand", or "I've been looking through the code I've written to deal with car valuations, I think I can speed it up a lot and reduce the load on the computers so we don't have to buy new ones later") and put it in terms he'll understand he'll know you're working hard.

Some people are shit managers. I should know, I are one :) Sometimes it's easier to manage your manager than the other way around.

Also your 20 days holiday is below the legal minimum.