Martin, try somewhere like HIC (www.hertsinsurance.co.uk). They should be able to insure you @ 23. They specialise in things like classic policies. The S2 would be covered as it is more than 10 years old and the cabby is more than 20, so would be covered as well.

You could probably get both for less than you are paying for one now.

I have the cabby and the 2000e insured with Peter D James Ltd (you have to be 30 to be with them though) and pay £222 for the pair, with agreed value and was with HIC previously with the 2000e, the cabby and the 4be.