If you can hear grinding the chances are that the pads are worn down to the point where the disks are getting damaged.
You might have gotten away with it but it's most likely new pads and disks
Disks can be pricey £50-£60 each but you can get cheaper pattern parts
http://www.widaonline.co.uk/
You can try some quotes from garages but they'll most likely want to get the car in to look betting that you'll say yes once they've got it in and have declared it unsafe to go elsewhere.
Alternatively order the disks and pads and get a mobile mechanic to fit them