Jake's answer is superb! Also, it would be a good idea to watch films in English to improve your understanding, I recommend watching a film in English with subtitles in your language or English. Later, watch the same film again without subtitles to improve your listening skills dramatically, if it hard to comprehend continue watching until you have a full understanding. I have tried this method with my students and also for self-studying in Spanish, it works very well. Make sure to include idioms and phrasal verbs, they are an extremely important part of every language and are necessary to take your language learning to the next level! I would also, as a teacher, recommend taking conversational classes with a teacher or finding a few language partners that you can practice with frequently. :) Good luck Gavin and remember to stay positive!

Vocabulary is the doorway to listening comprehension, as having seen a word before and trying to pronounce it in your head will let you better recognize it when it is spoken. Read the newspaper while using an online dictionary to look up words you don't know. Add common words and good words to learn to a flashcard application or write flashcards and study them every day for 30+min. By greatly improving your vocabulary, you'll greatly improve the chance of recognizing a word when it is used in speech. Then, the more you hear people speak, the more connections you'll make and the easier it will be to understand.