It may be difficult to track down the Artist specifically, unless you take it to a proper Galley/Museum/Auction House. You need to find specialist in these fields for concrete answers.
You have a dated Award of Merit by the looks of things also recorded on the picture, from the RHS. So they may be interested in or know something about this picture and the Artist who drew it.
In the past it was not uncommon for an Artist to find employ in the field of Encyclopedic Style Drawings. Usually hired for their attention to detail and accuracy of drawing. A lot of reference books would have used such artists to great effect before the onset of the Modern Colour Camera.
But to get things rolling here's a link you may find useful.
AskART - Art Prices, Art Appraisals, Art Value, Auction Prices, Art Database