Price of a first class stamp today?

36 p minimum.

this link is to the price calculator of the Royal mail.

http://sg.royalmail.com/portal/rm/PriceFinder;jsessionid=LJ4SJ5Y22B054FB2IGGUNZQ;jsessionid=LJ4SJ5Y22B054FB2IGGUNZQ?catId=23500532&gear=pricingcalc