@ Zait and Wass
Thanks for the tips. I have tried the other races but the Zerg is where I play with the most comfort. My injects are near perfect now because that is the first things I worked on. To help with that, I use the locations so at the start of the game I ctrl + F1-F4 my main and 3 expansion areas so I can just jump to them every time i hear the inject larvae sound when its over.
As for macro, i find it easier with good injects - I constantly just press 4 to select all my hatcheries then S and create the units as I am fighting. I don't always get it right but most of the time I do. I do have to agree about the builds though, I tried a few builds I seen online but they are a bit harder to stick to at lower leagues because your opponent can go for anything like 1 base Battlecruiser, which I actually met earlier today lol but I had him completely contained with Infestors and scouted his BC's before he could get more than 3 so mass corruptor sorted that out easily.
I don't have a build per say, but I do pay attention to timings and I do stick to my same opening in all games and it does work for me a lot of the time. Expand @ 15 against Terran or @14 against Protoss. Gas to get ling speed + double evo chamber, lair and 2 more gases between 7:00 and 7:30 then go mass Infestor/Zergling/Baneling and just add on a spire if I need to fight off air units or want Broodlords.
Thanks for the video link. I will check it out now as I am familiar with Destiny and Day9 but of course I have to take what they say in terms of strategy with a pinch of salt because low levels can be far from predictable. I do think I will get promoted soon though which is great because I am playing more and more gold level players and have about a 50% win rate against them and are even now marked as "Favoured/Slightly Favoured" against other Silver players!
PS: 15+ Infestors is REALLY effective in low league play