Rearsby's Roses - who found and registered this rose - appear to have ceased trading. The only reference I can find to them is a planning application for re-development of their property.
My plant came from Lady Salisbury's garden in Dorset c. 1999, and I have not seen it for sale since (though 2 nurseries have it on their catalogue).
Both Gregg Lowery (Vintage Gardens) and David Stone (Mottisfont Abbey) have seen it in situ and are happy with the attribution. It is a hugely vigorous climber - doing for 'Ballerina' what the climbing form of 'Mlle Cecile Brunner' does for its namesake.