This thread has brought up so many memories.
Shovelling up the manure from the delivery horses was something my Mum always did, for Dad's veggie garden.
About being ashamed of your Mum for no real reason at all - this puts you in good company - Alan Bennett - who is deeply ashamed now because he was ashamed of his parents as a kid, because they were not posh (Dad was a butcher)
My husband remembers being sent out to collect dog ends for his truly evil step father.(There were much worse things happening and the grandparents soon rescued him and brought him up)
Mum would have been devastated it I'd acted common in any way, but one thing she could not do anything about was my accent: I've always been 'broad Yorkshire' and not even going to grammar school could change this. I never gave a thought to the fact that a working class accent could affect the way you are treated though, until I went au-pairing to Vienna at 19, became fluent in posh German because I lived with a very posh family, and found that people had quite a deferential attitude to me.
Being common seems to be a part of every socioeconomic group nowadays, as you see from tales of the rich and shameless in the papers.