Everybody was descended from Charles II. You probably are too. He fathered a whole generation of royal bastards but had no legitimate heir. The Royal Family is indeed descended from the Hanoverians, but their claim to the thrones comes from Charles II's father James I. So this just isn't true about the Spencers.
Dinner with the gentry is usually formal. Grand dining room. Properly set table with wonderful china and glassware. Individual salt and pepper, usually silver - salt always in little dishes. Lots of bits and pieces of silver, some decorative or regimental. Cheese biscuits tend to come in a silver box. The whole rigmarole of turning first to the person on your right, and then the left. But dinner is always fish pie or shepherds pie. Nursery food. The really scruffy woman who looks as if she cuts her own hair and is wearing a cashmere jumper with moth holes and frayed cuffs is the marchioness and therefore the poshest. There will be several dogs wandering around: two shooting labradors and something small and not necessarily pedigree.
The drawing room will be comfortable - deep sofas covered in damask or chintz with Tartan wool rugs so that the dogs can lie of them. Piles of Country Life, World of Interiors and Shooting Times. Dog baskets. Lots of photos in silver frames with the royal ones arranged so that you can see them (but not too prominent because that would be trying too hard).
Sometimes, though, it will be kitchen supper. The kitchen is huge with a vintage 4 oven Aga and piles of clutter. There will be lots of le Creuset and more dog beds in front of the Aga. Baskets of iffy-looking fruit and veg on the side and piles of paperwork about farm subsidies. There will be a timetable on the wall with the booking for the shooting weekends entered in Sharpie.
The women are all thin, but not botoxed usually. The men talk about Eton - doesn't matter how old they are, they talk about Eton.
Daughters are interior decorators or work for auction houses. Sons manage rock bands or (if too thick) run the B&B side of the estate.
Cars are generic SUVs or ancient lands. A couple of Ford Fiestas as local runarounds.