Unfiled tax returns from 2006

liketoknow

Hi, I was going through a bad patch heathwise a few years back and didn't file my SA tax returns from 2006 -2007 to 2010-2011. I was paying PAYE on some of the income during that period. My earnings would not have been enough to pay tax on as I would have been under the personal allowance. I built up a credit of over paid tax which I have left in the pot in case I did get into a position of having to pay tax.
HMRC charged me heavy penalties for not filing the returns, which they took out of the overpaid tax.
On my statement of account, those five tax years are labeled as overdue but it says they can't be filed on line. The penalties have stopped being charged on them. I can't file the returns as the information has been lost when next door had a leak which came through into my house and destroyed the records.
What happens about those returns, I think I read somewhere that after so many years they don't pursue back returns, is that true? I have not had any letters about them for years.
I am past retiring age now although I have not claimed my pension yet as I am still working part time, nowhere near earning enough for tax payment - only around £5500 pa on last return. I could do with the overpaid tax returning as there is a credit on my account still of over £3000.
I have been filling in tax returns since 2011-2012.

Hope someone can help.