There must be private companies that do it. Like the ones that shipped my bike to Mal's house in Poland from my door for £32.
I sent a bike to Dublin last week for £46 having taken it to my local post office. Originally I had just removed the saddle and the front wheel but 'volumetrically' it would cost close to £200. I scrounged an old box from Halfords recycling skip and dismantled the bike including removing the chainset as it was too tall to fit the box. Once it was all in the box it weighed in at almost 16 kilos. The P.O website said it would be £43 but in the flesh it was a bit more. I don't know if this will help.
I sent a bike to Dublin last week for £46 having taken it to my local post office. Originally I had just removed the saddle and the front wheel but 'volumetrically' it would cost close to £200. I scrounged an old box from Halfords recycling skip and dismantled the bike including removing the chainset as it was too tall to fit the box. Once it was all in the box it weighed in at almost 16 kilos. The P.O website said it would be £43 but in the flesh it was a bit more. I don't know if this will help.