His will was dated 6th Aug 1799 with a codicil of 30 Nov 1799.  He appointed Charles Greenwood (grandson-in-law) and Thomas Round to be his executors.

His will was proven on the 27th Jan 1800.

I therefore conclude he died around Dec 1799.

The details of his will are beyond me to interpret as they rambled on in the usual illegible script!  But they seem to have left legacies to his daughters, his wife and a grandson Greenaway Jaques.  He held several properties and was obviously significantly wealthy.
________________________________________________________

The Sarum Marriage Licence Bonds Transcription has this entry for Elizabeth Beck as the bride:

First name(s) GREENAWAY
Last name JAQUES
Birth year -
Bond day 15
Bond month Feb
Bond year 1745
Marriage year 1745
Place READING ST GILES
Marriage place Cholsey
Groom's first name(s) Greenaway
Groom's last name JAQUES
Groom's age -
Groom's occupation bargemaster
Groom's parish Reading St Giles
Groom's county Berkshire,England
Bride's first name(s) Elizabeth
Bride's last name BECK
Bride's age -
Bride's parish Wallingford
Bride's county Berkshire,England
Bondsman 1 WILDER Edward,boatbuilder,Pangbourne,Brk
Jurisdiction The Bishop of Salisbury in Wiltshire and Berkshire
County Berkshire
Country England
Record set Sarum Marriage Licence Bonds
Category Birth, Marriage, Death & Parish Records
Record collection Marriages & divorces