Battle of the Nile L'Orient blown up Ex 1799
[From the 1793 RA Exhibition catalogue]...275 Battle of the Nile, at 10 o'clock when the L'Orient blew up, from the station of the gun boats between the battery and castle of Aboukir
275 was in the anti-room

[Redford]...............'Battle of the Nile L'Orient blown up Ex 1799', Date of sale: 1864, oil, seller: Huskisson; buyer: bought in; 10 guineas
[C.F Bell].............. 'Battle of the Nile, at 10 o'clock when the L'Orient blew up, from the station of the gun boats between the battery and castle of Aboukir' RA 1799 No. 275. Date of sale: 1864, oil, seller: Huskisson; buyer: bought in; 10 guineas
[Butlin & Joll 10]... is a long entry and covers the evidence for this picture in depth
[Christies e-mail]... Date of sale: the 3 Huskissons at the same sale hence April 27 1864, drawing, seller: Huskisson; buyer: bought in;
[The Art Journal]... n/a

This picture is lost. Being in the Anti-Room it is an oil but it's size and substrate are unknown. Four oils were exhibited in 1799. No. 305 in the Anti-Room was 'Kilgarran castle on the Twyvey, hazy sunrise, previous to a sultry day'; its size is 36" x 48". Considering the attention given to symmentry in the Anti-Room it is quite possible that 275 'Battle of the Nile' was the same size.
In the Great Room were, 55 'Fishermen becalmed previous to a storm, twilight' [Lost, 15" x ~30"] and 192 Harleck Castle, from Twgwyn ferry, summer's evening twilight' [34" x 47"].

B&J cat.No. 10 and C F Bell page 73 No. 89 provide the following information:

• Huskisson sale Christiies 27 April 1864 lot 91. B&J says, "at his sale of 27 Apr..." showing therefore that 'L. Huskisson' is a man. An earlier sale (1857) recorded in Redford vol 2 Page 128 shows the sale of Penry Williams 'The Ferry', at 152 guineas seller Mrs Huskisson, buyer Toms
• Regarding an exhibition of 'XIX Century Art Society' C.F. Bell gives the date as 1886 but Graves dates it 1888, shows the owner as W Cox and the place as Conduit Street Gallery
• Claims regarding other sales; Hugh Cholmondeley (Finberg 1964 31"x39") and Parke-Bernet New York, 2 March 1950, lot 41, from the coll. of Joseph Prior are dismissed by B&J.

So details about the sale and whereabouts of this picture do not directly shed any light on the 'St. Vincent's Rock Oil'.
One thing however is not given the weight it deserves and that is that the RA Exhibition catalogue (in the list of exhibitors) clearly lists the picture as a JMW Turner viz: 'W Turner, Hand Court, Maiden Lane' including No. 275 amongst his exhibits. It is unlikely to be a different Turner. It was not marked for sale in The RA Exhibition catalogue (So it was either already sold or returned to Turner and subsequently sold or given away in a series of exchanges that led to Mr W Cox's ownership in c.1888) (It may have been exhibited both years 1886 and 1888).
Another possibility is that W. Cox also aquired the above No. 5. St. Vincent's Rock, Avon, Bristol Ex 1793.

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The following is said by B&J to be a sea battle not by Turner