In search of flattering pants to wear under trousers

[Merguez]

Please help me! I am of a certain age and although not massively overweight, am a bit chunky in the thigh and bottom area. Was pleased to find some flattering black evening trousers yesterday but need to invest in better underwear which does not show and cut across the top of my thigh and helps flatten my slightly paunchy tummy (2 C-sections, many years ago, so no muscle tone there).
What will work?

[Merguez]

Anyone?

M&S seems to have a wide choice of control pants, but are any of them any good?

[70isaLimitNotaTarget]

Look in M&S or online.

I got some M&S Trouser Pants. They don't give support but are VPL free (I can't wear a thong at my age)

And they do have some 'control' ones (that I wear under leggings)

Would you be looking for high waist with longer leg style?

Maybe Spanx ?