I attempted to change the drivers side inner tie rod on the steering rack on my 2007 fiesta earlier. I have the tool but there are no flats on the old tie rod to undo it. I tried large waterpump pliers but the teeth on the rack started to move and I was worried it was going to break. How do they come off? The new rod has a male thread and flats to fit the tool to fit it.

Once the locknut is undone, they're usually not tight to come off. Try a pair of vice grips or stilsons to get better grip. Use lots of penetrating fluid if you need and maybe a blowtorch if you get really stuck.

stilsons is what I was thinking. in my experience many vice grips (mole grips) have soft teeth that don't cut in very well and just round off. 

Big grips or Stilsons is all I use. 

Thanks for your advice people, I finally got it off today, had mole grips on the rack and stilsons on the tie rod end and it came undone! The new one had flats on so no problem fitting that. Sorted, cheers 👍🏻