Today Ruby had a thorough examination by another vet,and thankfully her heart murmur does appear to be slight,hopefully given time may even disappear.
Many thanks for all your replies we received and advice given by others who had been in a similiar position in the past.Most appreciated.
Really good news, I am pleased Like Inca says, worth keeping an eye on it with the vet. Poppy lived until 13 with a heart murmer from the age of 8, as we caught it quickly and the tablets were essential to keeping it under control.