Actually, this is an interesting problem. I just sold my Avon Redseal, and had trouble finding a courier to deliver it to Cornwall. In the end, it went via Parcelforce 48hr for about £50.
The Interparcel site reckons you can send a 33kg Zodiac for about £16 with CityLink. But, if you look at the CityLink site, they say their weight limit is only 30kg. So, would it go for £16ish or not?
OK, useful to know for the future. My Parcelforce price included extra compensation up to £250, which I thought would be wise (having experienced Parcelforce before).