I have taken bits of what everybody has said and put it into action. So far i found out that patting, stroking, rocking, picking her up, putting my head in the cot, putting my arm in the cot and sitting right next to the cot doesnt work but (yes there is a light at the end of the tunnel) i have put her in and been sitting on the toy box opposite the cot (where she can see me when she rolls over onto her tum) and she protests but its more the whingy cry rather then that sad cry..so i sit and look at her and eventually she puts her head down, gets comfy and falls asleep. I have also been keeping the door open until she is asleep. So far, this is working pretty well.. but as u said Amy they change all the time. I guess then we try everything all over again.
Oh and on the night we had guests, DH fed her in our room, rocked her for 30mins (bit full on but we really wanted her to sleep) and she was out till 7am the next morning.(horray) So it all worked out.