One of the things that comes across is that all the actors bought into the project, the results are a brilliantly written script and executed with passion, conviction and sometimes humour by great actors.
Most of us at some point have felt Colin's pain and felt helpless to do anything about it. Colin (Winstone) articulates this for us brilliantly then confirms the only course of action.
They had to be gangsters because ordinary people with the same dilemma don't go around kidnapping the wife's lover otherwise not really relevant to the story, hence the 4 stars instead of 5, the trailers are misleading.
If you are offended by swearing give this a miss (the F word is used 167 times apparently) but if you are ok with it and enjoy a sharp, tight and sometimes funny script. It's worth a look and you may be surprised.