Regular scraping noise from rear

If the bikes that old, a caliper strip and rebuild would probably help no end.

Once you ride your bike you will probably find the noise comes back as stig said cos the piston will settle into it's position.

First run out will be this afternoon. I squeezed the brake a few times, but time will tell I guess. A sticking piston might explain the jammed pad.. I have yet to give the calipers a proper seeing to, only bought the bike midwinter and so far I've only done the things you can do with frozen hands. Need to go over the whole bike now the weather has improved, as far as I know it's never been given more than the bare minimum of attention.

Have been out a couple of times now and the scrape has definitely gone. I still feel like I can hear a change in the tone and feel a little more resistance in one part of the wheel's rotation, very subtle now tho, so I think something isn't perfectly straight. Thanks for your help everyone!