That is now fixed. Below is a few of the steps that I had to go through to get this finished. Unfortunately I didn't get all of the steps as this because one of those projects that just needs to get done and I forgot to take any photos.
With all of the holes opened out there was only a little metal holding the centre of the hole in place. To punch through those I put a house brick underneath and used a chisel to punch through the holes in the brick. What I should've used is a cold chisel. However I only had an old half busted wood chisel that needs a fair bit of time on the grinder before it will cut anything. Anyway because it was no good I just used it to punch out the little tangs that are left.
Of course this took a bit of time which could have been avoided if I'd drilled the holes a little furthur out rather than right on the line. However I did get a good bit of practice doing this and next time I have to peen something over like this I'll probably be a bit better.
Next steps here is to get a thing to catch the leaves as they come out of the gutter, then connect this up to some kind of tank so I can water the grass here without worrying about how much water I'm using.
If you want more details, have any suggestions or questions please get in tough or leave a comment below.