I thought that the new ones were based on the standard
charity ones,
whereas the old ones weren't? Re-using the old ones could then cause
us problems later when we go for charity status.
The old ones were based on the standard ones at the time, but those
have changed. To the best of my knowledge, the old ones were
absolutely fine at time they were written, they are no longer fine now
(they would probably just about work, but wouldn't be ideal). As
Alison says, I think the differences are just in the details, but they
are important details.