Cheap, quick screening

My neighbours have extended their house recently which means that it is now about 4ft above the level of my garden.  They are now building a large deck which is at the same level as the house.  They have also raised the level of their garden on their side of a 4ft block wall so that the garden is level with the top of the wall.  I have 3ft of trellis along the wall with a rambler rose threaded through it, but because the level on their side has been raised, anyone standing on the raised lawn on their side can look straight over the fence into my garden, and somone in one of the chairs which are on their lawn can still see straight through the trellis as the rose isn't very thick - especially in winter.  Although I have quite a large garden, I now have very little privacy.  I don't own the fence between us (apart from the trellis).  I don't have very much money and I need a very quick fix for this problem.  Any suggestions?