Pleased you’ve found something of use in the Will.
Re records at Kew. There are a number of records that may yield more data that it may be worth investigating further.
1] ADM 196 RN Officers’ Service Records. Although these are all supposed to be available online at the National Archives, I believe I may have found some exceptions that may interest you.
If you go to
http://www.nationalarchives.gov.uk/catalogue/search.asp and enter William Jones, dates blank, Dept ADM 196 - 4 records are returned all ADM 196/3 series - that’s Officers Time of Service; Date of entry: 1780-1851, Latest date of discharge: 1857.
Now open another window with your browser [Firefox just click a new tab] and go to
http://www.nationalarchives.gov.uk/documentsonline/adm196.as... , click search and enter William Jones all other fields blank, you get 37 records – comparing the lists and searching the 37 for records from ADM 196/3 – you’ll find 3 on page 4 [notice the ranks]. So it appears either not all records have been captured in the digitising or perhaps they are slightly different records. Worth checking perhaps. You can either email the National archives with a query pointing out the differences or from the catalogue search click on each record e.g. ADM 196/3/657 Name: William JONES; Rank: Lieutenant. Then click request this and follow the instructions to obtain a copy.
2] Lieutenants passing certificates in ADM 107 or Lieutenants Certificates of Service also in ADM 107, the latter being ADM 107/71 to ADM 107/75 covering from 1802 to 1848. These records sometimes have birth/baptism information.
None of the ADM 107 series can be viewed online so for you it would require the services of a researcher, from
http://www.nationalarchives.gov.uk/records/ scroll down to paying for research and follow the links.
Jeff