Item: 115579863874 is a good example.

As mentioned, this rate table is £5 / £12.50 /£21.50 but as the item is slightly heavier than the norm, trying to amend the existing rate table to £5 / £15.00 / £25.00 can only be done if saving the new listing into the draft folder - commencing the draft will then allow for the rate table to be changed for this listing only.