"loads of mistakes" is a perfectly correct and usable phrase in written English.
You can use it to refer to a situation where numerous mistakes have been made, either by someone or in a certain situation. For example, "John made loads of mistakes when he attempted to fix the fence."
If I could wish for anything, it would be for a compass that could go back in time, cos there's loads of mistakes I made.
And I'm realising more and more with old recordings that the reason they sound so honest and heartfelt, and recorded so well, is there are loads of mistakes.
I made loads of mistakes in coaching and I remember Gordon Banks saying to me: "Are you all right, son?" I said I was fine but I clearly wasn't.
"But it was a great game of football - loads of mistakes, loads of good attacking play, honest play but we've got to be a bit more professional at 4-1 I think.
It would have an amazingly creative atmosphere, with lots of collaboration and cross-over, where loads of mistakes could be made, but every so often something wonderful would be produced - a bit like Warhol's Factory, except that a lot of people there didn't really make a living.
"I've made loads of mistakes.
When companies genuinely apologize for a mistake, they gain loads of credibility with their customers, who are much more likely to understand that mistakes happen.
I may make a ton of mistakes, but I know how to properly load a dishwasher.
The configuration loaded by the positioner software limits the choices for these parameters, thus minimizing the possibility of mistakes.
Matthews also related that "I'm sure loads of people bought the record by mistake, but who cares?
I learned about the freedom to make mistakes, and something unexpected could come out of mistakes.
