I use Parcelmonkey, mate. Paid as little as a tenner for a full boxed bike. Measurements of box ultra important for final price...play around with different sizes on the online quote.
Wouldn't send a bike which is not in a full,proper bike box. Rear of Halfords favourite here.
Always been wary of " feel free to arrange your own courier" type deals. Not confident that someone who can't be arsed to offer delivery would make an effort packaging for my courier.
Had a bike delivered once wrapped in a broken down crisp box.
1993 Orange Prestige
1998 Kona Lava Dome
1995 Kona Cinder Cone
2000 Klein Attitude Comp
And a whole bunch of road bikes......