LindyR I'm not trying to persuade you to tell us, so please do not think that, but I immediately wondered, assuming you are in the UK, which part you are in. My reason being that I was born in the affluent home counties and around my 50s moved to the East Midlands. The immediate absence of snobbery was so beautiful! Indeed I only heard bits of it, tinged with what I assume they regarded as polite racism, when southerners invited themselves to stay over on their way on holiday further north!
I really feel for you! People like this right opposite your home it must be very upsetting. If you meet the woman who works in your field at another conference, I was wondering if you could just try persistently talking to her! Kind of go up to her and loudly say, "Oh Snobena! Fancy you being here! I could have given you a lift!" turning to the crowd you say "Snobena lives in my road, you know, she's quite well known in our neighbourhood."
To the bike-shovers just be short and to the point, "We haven't got room for your junk, thank you". If junk is too rude say cast-offs. Or the "My husband is an aficionado and we would not use that type of old bike." Then they natter on, so you repeat "My husband is a bike expert and we would never..." Just use the broken record technique, repeat repeat repeat...
As it happens, my daughter when living in London had the woman opposite (WO) come to her door and say "Will your husband come over and fix my gate as soon as he can?" (I think it was a gate - it was a while ago). My daughter, bemused, asked why the lady thought her husband would be any good at that. WO said, "Well isn't he some kind of odd-job man?" Actually he's a senior Partner in a famous group of Solicitors and they are living out of London currently, as he is doing Government work on a project frequently in the News. Well it was before COVID. People make assumptions!
I grew up in a feudal village with a Lord of the Manor living in a Manor House. Subsequently at his death his daughter succeeded the title and lost the Manor House to Inheritance Tax. She and my father, a lowly farm worker who was born on his father's farm which subsequently was sold, had known each other all their lives, having worked adjacent farms. We had an 80th birthday party for dad in the historic barn. The Lady of the manor, in jumper and trousers, was filling kettles to boil. My cousin's wife, in frilly blouse and high heels was swaggering around looking for the Lady of the Manor, to suck up to. At one point she came to us at the Food Serving area and totally ignored Lady X - clearly she looked far too common to be the Lady of the Manor! This is what I love about Princess Anne. She looks after her horses and cleans up the yard when she is not out doing great work for Save the Children etc. She never makes a big fuss nor tries to grab headlines. She is down to earth, caring and decent.