Wouldn't normally comment on this, but heard so much on these 'lifetime' warranties, I thought I would.
As per the Website in the link posted previously:
"Discontinued models - where a damaged rod is from a discontinued line, Hardy & Greys Limited may offer the owner a comparable rod from our current range. In these circumstances the owner would pay the £25 handling charge referred to above and 10% per section (1 or 2 pc rods) or 20% per section (3pc and above) up to the maximum of 50% of the current or last recommended retail price of the rod."
Therefore, it seems like you should be paying £25 handling charge, plus 10% per section (£300 RRP = £30). Looks like £55 total to me??
If they've quoted you £140 tell them where to go! As previously mentioned, all Greys (and other companies) sea rods are made in the far east for next to nothing. I have previously used them (Sea and Fly rods) and broken them. I know it doesn't really help at this point, but try to buy something different and half decent. (Century, ZZiplex etc). Doesn't have to be brand new. There are loads of good second hand deals to be had if you look for them.
Keep us updated on the situation and good luck!