Don't know of anyone who's done it from Cape Town to UK, but Chris Bright did it from Cape Town to New York, and his Cape Town contact details are on the Shipping page - see below for the link.
Travellers have had good results with Panalpina, who are worldwide. Their Cape Town address is:
Phone: +27 (21) 5506500
Fax: +27 (21) 5511973
We flew our bike from Cape Town to Buenos Aires in November, 1997, with South African Airways cargo. Don't know what the rand is worth now, but our cost worked out to US$1,000. for 559 kg in the crate.
Hope this helps.
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