Just looked at Aviva and Nationwide policy wording. Although riding your own bike over 125cc is covered, they both say you're only covered if "and you are wearing suitable protective clothing.", now who decides what is appropriate? Riding down to the beach in Spain you're not going to put full leathers, motorbike boots and back protector on - are you?
No but you will wear a helmet and hopefully not flip flops and trunks. Why dont you ring them for clarification?