John Humphreys outlines our knowledge about William Dickson's early years:
After having been recorded at birth (1762), he reappears at his marriage (Manchester Cathedral, 1786, a "yarn merchant" aged 24). Where he had been in between, and where he went afterwards is unknown. Adverts in Manchester papers tell us that William Dickson "has removed" (24 Mar 1789) from
Crow- Alley
to a warehouse in
Cromford-Court
, where he offered for sale Cottons from "Brazils, St Domingo, Tobago, Grenada and Smyrna".
In April 1792 William Dickson offers a range of cottons to be sold at auction at the Bull's Head, Manchester (on Tuesday 24th April at three in the afternoon). This is followed in May by a sale of some cottons by private treaty, by Mr William Dickson of Cromford Court. William Dickson of Cromford Court, a cotton merchant, is listed in a Manchester directory of 1794, but not in the next one, 1797. We can't be sure, though, that all of these sources mean the same William or different ones.
Similarly it's not quite clear when he moved to London, though his son's schooling in Hackney 1801-1804 might set a time frame.