] Are we assuming a date of 1811 for the setting of the book?

No. At least, I'm not. Here's a link to an earlier thread on the dates of P&P (and also of Jane Eyre, but people can skip that bit).

According to my calculations, the best fitting date is 1800, but I'm willing to accept that JA purposefully abstained from dates. But not 1811-1812: it won't do (and I know Chapman said it would, but he got his sums wrong).