Hi Silvertones and Bob,

Thank you for your helpfull advice which will enable me [and others]to avoid paying duty in the future.
Previously, I have always opted for a flash drive version to avoid the possibility of a download crash and also because with numerous previous PG purchases on CD or flashdrive I have never before been charged duty. Presumably HM Customs have changed their duty policy recently. I got caught this time but hopefully now others reading this in the future will not.
Regards,
Peterj