Hi
So, you have sent your lba?
You have not filed a claim yet?
When can you file your claim (2 weeks after sending your lba)? I think what you should do is send them a letter stating accepting their offer as part payment and state the date you intend to file a claim, along with this attach a schedule of charges with a schedule of interest for each charge ( until you take them to Court, yes! this is a
letter before action, so you
are intending to take them to Court

). Then file your claim on the date you specified.
If you don't want to go for the interest (work it out and see) then just settle, it's up to you but that extra just may be worth it!
Wxx