First find out your broadcasters specs. 720p is rather rare...you will probably be required to do 1080i50.
If you want a quality job, master to tape in NTSC and have it converted on an Alchemist (or other high quality hardware standards converter) to whatever PAL format is required. This cost money, but is real time and will give the best results. Any software conversion will be inferior and may get your master rejected by the broadcaster.
If you are on a small budget, have no choice and need to do this in Compressor, you will want to export as a Quicktime movie from FCP (same as source..or Pro Res 422 or HQ). Take that into Compressor, set up for whatever your PAL delivery requirements are. You must turn on the Frame Controls and then set the resize to Better or Best (if resizing to 1080...leave it at fast if staying 720p). Set the Rate Conversion to Better or Best. Best does not always yield the best results, as the Optical Flow algorithm can be fooled by some types of footage. Do tests. And pray.
You can also purchase the Standards Conversion plugin from Nattress.com. Its much faster than Compressor, but a little tricky to use. Only 99 bucks. It works within FCP, usually does a good job, but its no Alchemist.