We just renewed our UK passports, apart from DHL couriers being a bit rubbish we were amazed.
UK website process was a doddle, so easy I double checked it wasn't a scam site.
Post Shop were very helpful and made sending them painless.
From sending passports off to getting new ones, less than three weeks. Did not cost much more than son paid to renew his in UK.
NZ immigratin on Queen Street were very obliging for the visa transfers letting me drop them off and calling me when they were ready. A different experience all round.
DHL were a pain. they left two 'you were out cards' with no names on them so we had no way of knowing what was being delivered to whom. Then they did not redirect my wife's passport because she has different surname to me.
Simon