Pixelation when exporting footage from FCP

Hey Guys,

Hope you can help...been trying to research this answer but only getting half way there.

I'm quite new to shooting with DSLR and using FCP so bear with me.

I used a Canon 550d to shoot some stuff in 1080p24.

As I understood it, the codec was H.264 which was not an ideal editing format for FCP.

So, using Philip Blooms tutorial, I converted my footage using Mpeg Streamclip into XDCAM EX 1080p24 (He gave the option for both this and Apple Pro Res but I was worried about the file sizes of the latter)

Editing in FCP with this conversion type has been fab...hardly any rendering...

But now I'm stuck with exporting my final video.

I did a basic export using Quicktime Movie and it's pixelated.

Any ideas on getting the best possible outcome?

I'm looking to have the highest quality, full HD version and also a web format for online use.

Any help much appreciated.