Thanks all for your replies, I appreciate you taking the time to share your experiences.
15 quid is over estimate on my part, I actually paid 11.99 for original shimano resin pads.
I used to be an advocate of superstar/disco/etc but I have since found original pads to be much better life and value. I haven’t monitored it scientifically but on a trip to Portugal a couple of years ago I went through two sets of SS pads pretty fast, and the originals I paid through the nose in a PLBS were still on the bike a year later after two more big mountain holidays.
Given the very mixed reports and methods here I am not confident that they can be fixed. I think I will bin them, take the 11.99 hit and self flagellate for a couple of days to teach myself a lesson.
Thanks again all of you for your input.