[Arran]

Arran Wrote:
Sometimes it helps to ad a small dab of fresh solder to the tip of the iron or gun whilst trying to heat up and remove the old solder as well.


That's because you get some flux on your iron from the new solder (there is flux inside most solders) and it heats up he solder faster, easier. That's why I suggested using some extra flux. he could try that but if still hard some extra flux might be the trick.

 It isn't strictly the flux in the solder but also that the clean solder can make better thermal contact with the terminal to heat up the crusty old stuff.
Regards
Arran