I had a look at ba flights to canada the other day and they seemd ok pricewise. Looked again today and the price has shot up. Is this ba policy that if you show interest in a flight they put the price up?
No. its called load management. Several others must have looked at the flight as well as you, but unlike you they decided to book.
BA (and every other airline) keeps a careful track on the rate that flight seats are being booked, based on stats they keep on optimising their income versus getting the flight full. If the flight bookings show it's getting fuller than they expect the price goes up. The reverse is also true.