Hi there,
I would stand your ground in that when you started your claim it was based on 6 years figures. The fact that they have delayed action in settlement does not negate the date of the claim when you first made it.
I would quote the date on which you first began your claim - and that this is a valid date and when action began so therefor falls within the limit of statutes for claims. i.e when you start the action and begin to pursue a debt.
I would refuse their offer - and pursue and think it is very cheeky of them to underestimate you and think you are willing to back down now.
The letter of rejection letter can be found here -
Rejecting Offers
I would use template 1 - it clearly identifies when you began the claim which a judge will rule in your favour as the date of first beginning negotiations and the settlement process.
Don't be intimidated - you are correct - they are merely arguing to save a little money.
Good luck!