Looks like I've found the answer. I somehow missed a previous post about this issue but have now read it and tried out the suggestion:

su-to-root and:
'modprobe ehci-hcd'

Having done the modprobe, /etc/fstab now contains an entry for /dev/sdb1 instead of /dev/sda1 and the reader now transfers at 2.81MB/sec - 40% faster than window's best speed

Excellent!

Pete