Although no dates have been found in any of the Pocket Love Library or Pocket Romance Library issues indexed so far, we can use the cover price values to estimate when the issues were published.
Issues of Pocket Love Library up to #14 have a 1/- cover price whilst #17-#26 have a 6p cover price. So it seems reasonable to assume that somewhere between #14-#17 was when Decimal Day (
https://en.wikipedia.org/wiki/Decimal_Day) occurred. This places the Pocket Love Library series around 1970-1971.
The cover price for issues of Pocket Romance Library (#27 onwards) gradually rise from 6p to 12p.
More issues may remain to be documented.