Thanks very much for the link. It provided some interesting reading. There were 2 reports on Kelso: one up to 1799 and the other from the 1830s. Unfortunately there wasn't one covering the period 1800-1810, however much could be gleaned from the available reports. In particular the fact that shoemakers were by far the most numerous of the trades in the late 18th century but, at the same time, appeared to be in a reasonably good position financially with their goods sold mainly locally and in bordering areas.
There was a comment in the second volume that mentioned that the growth in Kelso's population, though mainly down to the movement of people from surrounding agricultural areas into the town, consisted to a great extent of older people and that many young men were leaving the town to find work elsewhere.
Other than that I couldn't really identify anything that would specifically account for my forebear's relocation to London. I'll keep searching though.
Many thanks for your help...