safari 9.0.1
I have a Sainsbury's Online Bank Account. Access to the account is fine via my son's iMac which is running Safari 6.1.6. It is also ok via a MS PC running Windows 8.1. When I try to access my account via my iMac which is running OS X 10.10.5 and Safari 9.0.1 it comes up with the error "Safari Can't Open Page".
I have spoken to Sainsbury's tech support and they say no one else has reported a compatibility problem. At their suggestion I have deleted Sainsbury's bank as a book mark, cleared internet history and ensured cookies are enabled. They have also suggested switching to Chrome, but would prefer not to as I am quite happy with Safari for everything else.
I am completely baffled and would welcome help.
iMac (27-inch, Late 2013), OS X Yosemite (10.10.5)