domestic hot water too hot

I have a boilermate 2000. I've been concerned about the temp of my domestic hot water from the taps ever since i've had this house/boilermate 2000 (about 6 years from new) - however, finally decided to do something about it.

The system generally performs well but the water from the taps is always too hot (as an aside, i run the boiler at about 80% on its temp scale to force the store down to a temp of about 68 degrees rather than 76 or so; but i know this is not recommended nor the proper solution...)

here are the stats:

the system store is currently at 68 with the high and low trigger points at 68 and 61 respectively. This seems to me acceptable given the way I'm running the boiler.

the plate heat exchanger return sensor is reporting a general steady state of 64 (incidentally, if you press SW1 while viewing this figure there are figures of 70 & 75 shown on the LED, but these are not documented in the manuals - what are these numbers?)
When hot water is drawn the PHE value drops to about 42... Again, I'm no expert but this would seem like reasonable behaviour.

The DHW sensor reports a steady state (i.e. when nothing is in use) of about 60/61.. when hot water is drawn it dips initially to about 49 but then climbs rapidly to about 65. If i understand this correctly, this means water at 65 degrees is coming out of my taps. (and it feels on the verge of scalding). This is where i am confused, as the manuals state that everything in the BM is automatic and that it maintains a temp of 55 degrees... so what's going wrong here and how do I get this temp down.

the appropriate LED bars and LEDs come on and off as expected.

I can hear that the DHW pump is humming when DHW is being drawn - but listening closely i can't be sure if it's actually working or not (i.e. pumping) - could this be the problem? or could it be something else? Water temp is always good and consistent.

The IC on the circuit has a label saying CB ver 29/01 - if that's relevant.

cheers
nik