Mine was sent to Peterborough too and I’m about three weeks behind you with dates of documents being received, except that there was then an 8 working-day lag between my passport being received (29 Aoril) and it entering the processing queue (12 May). It is just possible that since yours involves a name change there may be a need for some sort of additional verification during the processing; but you’d have thought the marriage certificate would be sufficient.
I sympathize with your frustration. It is a black hole about which none of us can do anything. I am pretty sure they do have a better idea of processing times at present but have been instructed to give a blanket answer to anyone calling or contacting them in order to prevent any applicant trying to place pressure on their staff. It’s worth bearing in mind that the person you speak to can be attached to any one of the UK passport offices and won’t have any local knowledge about the office your application is at.