Billinge Maternity Hospital Records 1969

Hello, Can anybody help me find the whereabouts of the Maternity Hospital Records for 1969 please? I have been trying to find them without success. Having contacted Wigan & Leigh Archives ( I thought I had cracked it!) they tell me they only have registers for births at Billinge from 1911-1935. (which is quite amazing!) However, they don't seem to be able to tell me where the records are after 1935...
Any help I would be most grateful, as I have been trying to find these for years now!

Before 1974 Billinge was in Lancashire. Try the records office at Preston.