Thanks to Chris for looking into this so promptly.
For those interested, this was his reply:
"The original order from November didn't complete, unfortunately there aren't any error messages to show why. The more recent one has gone through and you are on the up to 20Mb service now. Due to the length of your line it's unlikely you'll see much of a downstream speed increase, however your upload should now be faster than previously. "
and my observation : correct, no increase in download speed [c3.4Mb], upload has increased from around 0.3Mb to 0.9Mb