This is going to be pretty useless, but ...
I've sent both whole bikes and frames by courier and I didn't find it hard to find a carrier. I boxed it up, measured and weighed the box, went on the web and found a courier to pick up from my home and deliver, but (and here comes the useless bit) it was a long time ago and I can't remember who I used or how much it cost. I think it might have been Parcel Force.