Thanks for the reply gubar!
I have another question though, if anyone can help.

1. To get the rounded end, I projected a semi-circle onto the extruded surface and then trimmed away the bit I didn't need.
2. for the surfaace at the end of the extrude- I extruded the semi-circle and then did an intersection which worked, but I ended up with 3 surfaces...
3. The problem is that I actually have to bevel all the edges, so I was thinking that I need to join the surfaces up somehow- but I can't work out how to?! Can you 'weld' nurb vertices together or something?