It's possible, if you speak nicely to PLD and have a special need for early issue, that they may be able to issue your licence earlier.
There is a backlog of applications, many applications are rejected the first time due to admin errors - and the CAA will check your logbook carefully to ensure that everything is correct. The time taken to process and issue a licence is factored into the overall CAA cost (it isn't a government run charity), so everything has a cost. The PPL used to be reasonable value when it was a 'lifetime' licence (as is the NPPL), but the 5-yearly JAR-FCL re-issue requirement is a complete rip-off.
No-one can legally fly with passengers until they physically hold a licence; merely passing the PPL Skill Test is insufficient. Whoever the 'CFI of the large flying school' was, he condoned an illegal act if he 'signed off' a pilot to take his girl friend flying an hour after he passed the skill test - unless there was also a FI on board as PIC.