I watched the first two episodes on PBS here in the States. I found the plot convoluted and confusing. The poor direction, where it was not made clear who was who and what people were looking at, did not help. Reading recaps for episodes 3 and 4 encouraged me to not waste anymore of my time. Use "Guilt recap season 2 episode x) as a search term and you get recaps by WTTW and Real Mockery. As I feared, it gets way worse in the third and fourth episodes. Read the comments on Ep 4 on realmockery and you get an idea how confusing and poorly done the show really is. I left a similar review there, but it contains spoilers.
It is obvious it requires about 3 or 4 re-watchings to even have a dim comprehension of what is going on. When the Eo 3 and 4 recaps alluded to absurd situations and even more convoluted nonsense, I knew not to bother with this show.
As to what drug the writer was on, I first thought methamphetamine, but it really didn't have that "Some Call it a Slingblade" clarity, so my bet is alcohol and cocaine. That famous painter said his painting was not done until he had nothing more to take out. This writer felt the screenplay was not done until he added even more unbelievable coincidences, implausible behaviors, and incredible motivations. The writer is a sociopath to do something like this. I am sure he goes to his Edinburgh cocktail parties and brags how is scripts are "abstract" and that the viewer has to invent his own interpretation, which makes the show special and invests every viewer a different way. I think he is lazy and too incompetent to tell a coherent story, and he was indulged by the producers.
The notable thing about this SE02 series is that every single character is despicable. I see a lot of British screenwriters that are misogynist, but this guy hates everybody. I wanted to take a cricket bat to everyone but Jackie's dog. I guess if you live in privilege and don't really know any real people and real situations, you can write stuff like this so you can amuse yourself looking down on the human race. I need something a bit more uplifting, sorry.
As to the people who liked the show, I see it as a form of Stockholm syndrome. You were kidnapped by the superb acting and good dialog. Then as the continuous confusion abused you, you felt you deserved it somehow, and it was actually a good thing. If the producers reined in the writer on the absurd plot and execrable exposition, he was capable of doing great dialog. It is a case of great tactics and lousy strategy. Kind of like the wars in Vietnam and Afghanistan, or letting a sergeant replace Eisenhower in WWII. I suspect this show will not do very well in the ratings, and would only get a third season if the producers are as disconnected from reality as the writer and director.
If you want a great show with straightforward exposition, watch the Australian police procedural City Homicide, maybe start with The Return, S01 EP04 (free online at Tubi and YouTube and maybe IMDb for all I know). You always know who is who, but there is still a mystery to be solved. I rate this show up there with NYPD Blue, made great by former cop Bill Clark, who kept the screenwriters honest.