an alternative just came to me…
got to file media manager,
a dialogue will open up,
that says
media:
a drop down box is underneath
select the "make offline" option
another drop down box specifies new codec to be used
set sequence to:
selct hdv 1080i 50
and finalcut will then make a duplicate of your sequence but disconnect all media, save this file as something different and then simplly do a batch capture.
ta da!
your original file will be safe