So, after a week of taking apart, cleaning, greasing and putting back together countless times then test driving, which was the fun part until we realised they still squealed, and hours of googling, it seems because our break pads are performance pads it is very common for them to squeal in normal everyday driving as they are made for heavy breaking, it's completely normal and nothing we can do apart from changing the pads!
Looks like we will be buying some new pads very soon. In the meantime we have been told if used in very heavy breaking (70mph very quickly down to 10/20mph) a couple of times should help them stop squealing for a while.
Thanks everyone for the advice it was very much appreciated