Deinterlacing is often advised as a way to fix basic field order problems in the workflow. Bear in mind you will be reducing your overall resolution with deinterlacing.
Try sorting your field order issues as deinterlacing will not make slo mos as smooth as interlaced done correctly.
DV is the only lower field order PAL codec. A lot depends on how you are exporting your quicktime from the sequence. Using Compressor to make the final mpeg is good but what are your settings in the original edit sequence and the QT export. Also are you using Qt conversion?