The garage weren't wrong. Look at the state of them:
Nice and new, cleaned everything too:
£300 for new discs and pads front and back is actually really good.
One down, I'll do the other three on the weekend. Very easy job though, I'm surprised. No seized or rusty bolts, no problems pushing the pistons back in either. I pushed them in by hand by using the old pads. From my experience I've always had to use a g-clamp to put pistons back in!
I suppose you get what you pay for