I have sold pens at craft fairs from Cornwall, to kent, to Southport, Glasgow, Yorkshire and about every county in between. Sorry Walter, never sold in Northumberland! I have not experienced any significant variation in sales volumes of any type of pens due to perceived or factual variations in apparent regional wealth.
The pens that tend to sell well wherever you be, are those which you like best and therefore express most confidence about. For a long while I did not like the Cigar or Euro, and surprise surprise, I didnt sell many. When I was asked to make a cigar for a very tall and large frame lady. The pen was in shocking pink acrylic and she loved it, as did her friends and I had several subsequent orders. It renewed my confidence in the pen and it is now one of my middle volume sellers. A similar story happened with the Euro, I thought it looked out of date, but the more senior of our population appreciate the traditional lines.
If you think the streamline will sell well, surprise surprise, it will, and if you think it wont, then another surprise?