Statute Barred Debt Scotland

Hi there, looking for some advice please.

I had a student overdraft of around £3000 which I defaulted on in December 2010. It was passed on to a debt collections agency and they have been sending letters and phoning since then. I really want to sort out my credit rating and was worried about court action just as this default is about to fall off my credit file (therefore ruining my rating for another 6 years) so I decided a couple of days ago that I would make them a full and final offer of 20% of the balance to close the account. However, I have just found out that the statute of limitations is 5 years in Scotland and not 6 so I could've taken this route instead. It was an email I sent them with the offer and not a signed letter.

My question is will this email count as acknowledgement of the debt and reset the clock even without my signature? Or does acknowledgement of the debt have to be within the 5 years so this email wouldn't count?

Thanks for your time.

Jay.