Where can I go for a night time picnic with my gf on v.day in berkshire?

Ok so valentines day is coming up and I dont want to do the normal thing of dinner and a movie, so im gonna prepare a picnic for us to have after work. Im going to by a glade candle thing (off the advert with the man in the bath, you know what I mean?) and try and get some silly pop up tent, as some shelter... becase it is febuary!! I wanted to go by the river somewhere but I want somewhere quite reclusive and quiet so we dont have distractions and we can just enjoy each others company, but I dont know where to go! I need somewhere in berkshire, someone please help???