You get to them near the bottom of the first page
http://www.autotrader.co.uk/search/used/cars/renault/megane/postcode/fy41da/radius/1500/keywords/250/sort/default/engine-size-cars/2l_to_2-5l
Don't worry I've changed my postcode
;)
The only difference between single and double pressing is the dead locks. Without deadlocks if someone was to break the window they'd be able to unlock the door from the inside; with deadlocks they couldn't.
I always double pressed.
Edit: too slow!