HCR diary 24.11.1821 party at Aders "Also a Mr Harcour (or some idem sonam) who is said to sing well and has a modest and sensible air"

                    29.11.1822 at Aders "Mrs Harcourt a niece of Aders was just arrived - a very plain woman but she looks amiable and Mrs A: says she is accomplished"

HCR diary 25.11.1842 at Basil Montagu's - Haldane's father was stopped from preaching in Aberdeen over forty years ago

Presumably James Alexander Haldane (DNB 1768-1851) father of Alexander Haldane (DNB 1800-1882)

HCR diary 9.5.1838 called on Aders "He tells me that Halcomb the Dover candidate has taken up the cause of Mrs Leigh"

                   8.7.1838 "I hear from the Aders that Mrs Ley has returned to her old house where she means to open a school -she has a friend in Halcomb the barrister!!!"

HCR diary 2.2.1827 "Gotzenberger the young painter from Germany called on me and I accompanied him to Blake - We looked over Blake's Dante. Gotzenberger seemed highly gratified by the designs and Mrs Aders says G: considers B: as the first and Flaxman as the second man he has seen in England. The conversation was slight - I was interpreter between them and nothing remarkable was said by Blake - he was interested apparently by Gotzenberger"

HCR diary 10.6.1824 at Gillman's Highgate (where Coleridge lived) "there we found a large party - Mr & Mrs Green, the Aders" &c &c

                    11.5.1825 "I dined with Green - Lincolns Inn Fields - a large party - Mrs Aders" &c &c

                      8.6.1826 dinner party at Aders "the Greens" &c

HCR diary 5.11.1824 "Mrs Aders, Ellen, Miss Denman and the Miss Gunns called on me - Not a little worried by such a visit I accompanied them to the Royal Academy Somerset House"

                    8.11.1824 party at Aders "The Flaxmans with the Miss Gunns and old Stothard"

                    20.5.1828 "The Rev Mr Gunn and his son breakfasted with me"

HCR diary 10.11.1817 "I stayed with Aders till late and gave him directions to buy a number of engravings for Mr Gurney"

Probably?  Hudson Gurney (DNB 1775-1864)

HCR diary 8.6.1828 "called on Aders - a Mr Goldschmidt was with him, who took us to see some fine paintings on sale in Leicester Square, belonging to Signor Reghellini di Schio"

                 4.11.1833 "went to the Aders - an agreeable evening there - Mr Goldschmidt was there - He has proved a very generous friend"

Possibly Adolphus Goldschmidt?

HCR diary 13.1.1819 Mrs Opie / Fuseli / Sidney Smith / Samuel Rogers (I just made that note with no more context)

                      4.4.1823 after seeing Aders' pictures, Sir George Beaumont "proposed bringing Fuseli"

George Beaumont (DNB 1753-1827) and Henry Fuseli (DNB 1741-1825). I've no idea whether Fuseli did visit Aders' collection

HCR diary 1.7.1842 at Samuel Rogers' breakfast table "Mrs Forster daughter of Banks the sculptor"...."and her daughter Mrs Poinder"

Edward Forster (DNB 1769-1828) writer married at St George Hanover Sq on 3.8.1799 Lavinia Banks. Emma bapt 20.5.1801 St George Hanover Sq dau of Edward & Lavinia Forster, married at British Embassy Paris 26.12.1832 Ambrose Poynter (DNB 1796-1886) architect. She died 1848, Lavinia nee Banks may have married again? (Lavinia Forster marriage index 1837 Kingsclere Hants).