Great work dude, keep up the good work.
BSE seems to have changed the HTML code slightly. Need to update those XPath selectors.
This is the worst part of a programmed scraper, I have a scraper for Screener.in that scrapes EPS and Sales data and there too I face this very same issue every few months.
Changes:
Purpose selector id has changed from @id="ContentPlaceHolder1_ddlPurpose" to @id="ddlPurpose"
Submit button id changed from @id="ContentPlaceHolder1_btnSubmit" to @id="btnSubmit"
Download link selector changed from //[@id="ContentPlaceHolder1_lnkDownload1"]/img to //[@id="lnkDownload"]/i
Trying to escape the rat race :P