A little bit of an update, the other day driving home my ST start to hum rather loudly from the back end. I knew the rear caliper wasn't 100% even after being fixed, but this sounded very much like a wheel bearing.
So today I had the car checked, and yep the other rear wheels bearing has gone, and the N/S brake caliper on the rear isn't working well. So hopefully tomorrow I will have a new set of rear discs, a caliper, and wheel bearing all sorted (fingers crossed).