Thanks for all the replies, yes losing 6months from a 10 year passport is small-change in the grand scheme, but all the same if one pays for X, one expects X and not X-5%, especially as we are obliged to renew our passports due to entry requirements.
I'm glad to hear that the turnaround times are reasonable, but as noted it makes planning travel, or for that matter unexpected travel, difficult. Has anyone used an expedited service whilst renewing the UK passport and would share their experience ?