If you have sent a letter acknowledging these debts to your creditors within the first Six years of a period of non-contact, payment or acknowlegement..... then you have re-instated the legal enforceability and subsequent recovery process of these debts again by restarting the Six year time cycle, as the debts never acquired the qualifying conditions under the limitations act.
You will have to check your records very carefully, but as you state you have sent an acknowledgement before year Five on 14/2/08 then the Six year cycle began again on that date.....hence meaning they would have to undergo a full further Six year period of non-payment or acknowledgement... before they could become statute barred. This would not be until 14/2/2014 a further full Six years, you would probably find the creditors will pursue these debts again or apply for CCJ's before then, which it would appear they seem to be entitled.