Money isn’t the primary class determinant!
Bridget Jones is based on Pride and Prejudice — Mark Darcy is ‘above’ Bridget’s family of origin as Fitzwilliam Darcy is ‘above’ the Bennets. Lizzy says to Lady Catherine de Bourgh that she doesn’t think she would be ‘quitting her sphere’ in marrying Darcy, because he’s ‘a gentleman’ and she is ‘a gentleman’s daughter’, but there’s considerable difference in status between the Darcys, who are established landowners, an ‘old’, though not titled, family with a big estate that has clearly been in the family for generations, and the genteel ‘small rural gentry’ Bennets (and Mr B has to an extent compromised his own class status by marrying the daughter of a small town attorney, as Darcy is aware.)
Similarly, both Bridget and Mark are middle-class, but from different niches within the middle class, but, like the Bennets and Darcys, not divided enough not to socialise together occasionally, whether at Assemblies or Turkey Curry buffets. But Mark is definitely recognised as a cut above the rest at the buffet, by the LMC characters, as Darcy is at the Assembly ball. Both Mark Darcy and Fitzwilliam socialise with people ‘below’ them — Darcy befriends the ‘new money’ Bingleys, whose money was made by their father in trade, and who don’t have their own country house and land.