11.6.1806 dine at Johnson's w. mrs Johnson / 2.7.1823 call on mrs Johnson, Eastcheap

Could have been the wife of Joseph Johnson's nephew Joseph. He married Alice Sutton at West Kirby, Cheshire in 1797 and their children's births were recorded at Bryom Street Baptist church, Liverpool. If not her then probably not a relative of Joseph Johnson's

11.6.1806 dine at Johnson's w. Conrad

Not a clear identification but a rare surname
John Frederick Conrad bach = St Dunstan i t West 2.8.1789 Ann Catharina Vocker sp banns sigs wits John Webster, Elizabeth Kramer
1790 Conrad weaver Norton Folgate
Holdens dir 1805, 1811 Mr John Conrad Queens-row Islington
John Frederick Conrad bur Bunhill Fields 9.3.1836 age 77

22.5.1806 call on Spurrier, w. M[ary] J[ane] / 23.5.1806 call on Spurrier / 10.7.1828 call on Lodge adv. Spurrier

John William Spurrier esq SunFire 1828 25 Old-sq, Lincolns Inn, will PCC 12.12.1848
John Spurrier auctioneer Copthall-ct Throgmorton-st SunFire 1781, 1785, 1789 & Yardleybury, Herts 1802, 1806
Isaac Spurrier coach builder Greek-st SunFire 1789 voted Sheridan & Paull 1806 will PCC 20.9.1827

30.4.1806 call on Willoughby (Nic)

Shropshire Archives 3614/8/38 letters of administration of Mary late wife of Nicholas Willoughby of Queens Row, Pimlico 13.8.1825.  But it would be unusual for Godwin to have used brackets after the surname for the first name, it more often referred to something the person was known for, like an address or an author's work - perhaps in this case being short for Nicholson, Godwin's friend who was at that time in and out of debtors' prisons

Holdens 1811 directory:

12.4.1806 call on Joachim (not seen)

Possibles

29.3.1806 S Burnel calls / 8.4.1806 S Burnel dines / 22.4.1806 meet S Burnel / 6.5.1806 E Burnel at tea / 11.7.1806 meet S Burnel / 19.1.1808 miss Burnel adv. at dinner / 12.7.1812 meet E Burnel / 16.5.1828 Breakfast, Reynolds's, w. Burnel

I made lots of notes on families of this name but don't seem to have found any plausible identification yet

9.3.1806 dine at Wimbledon [Tooke's} w. col. Stuart / 13.7.1806 dine at Nicholson's; adv. col Stuart & C[om]be

5.3.1806 Mrs Potigny at Taylor's

Couldn't find any other mention of her

2.2.1806 dine at Philips' w. Major Reid

No good identification.

Morn Chron 14.10.1806 died 9.10.1806 Major John Reid of Madras Infantry lately arrived from India.
Holdens 1811 directory Major John Reid 29 Aldersgate street. SunFire 1800, 1803 John Reid distiller Fan-st, Aldersgate-st. PCC 8.2.1836 John Reid distiller of Aldersgate-st, wife Lucretia, house at St Albans

Lt Gen Read 17 Lower Brook-st & Crowood, Ramsbury, Wilts

20.1.1806 General adv. at theatre

Could have been any general!