Having looked this up, its difficult to ascertain what's best for this one - the advice for patio and miniature roses generally is to cut down to 1 or 2 inches high - but no specific reference for the climbing form of patio rose. It might be worth contacting a grower/seller of this and asking them what's best to do.
On the other hand, most climbing roses ARE bare at the base, it's the nature of their growth habit. People get round this by shortening some stems to a few inches and leaving the others longer, or by training the stems sideways to encourage lateral growth nearer the base.

Thanks very much for your help with this & sorry for not responding sooner. The rose is now a mass of young shoots and I've decided to trim the higher stems to maintain a height of no more than 6.5 feet.

Thank again for your help