I purchased a TR HR-01plus for my less than SPCR friendly AM2 6400+ and I am getting really bad ( worse than the stock cooler ) temps . On removal of the cooler I found that an area at the centre of the heat spreader ( about 2cm diameter is not making contact with the base of the cooler due to the concave base on the HR-01 plus .
The temps I am getting are - idle 50c - 55c and under load I shut the machine down when it got to 65c .
What , if anything can be done to fix this ?

my best guess would be to lap (sand) the HR-01's base until its flat and smooth, or at least much closer to the shape of the CPU. you might also try the penny trick. that's where you place a penny between the IHS and the base of the heatsink. i'm not sure if this would help much though.

i'd research lapping and how it can help you, but first and foremost, put the stock cooler on so you have hardware left to work with.

I have already tried spacing the mounting bar with a flat washer ( I am in Au no pennies here our dollar is so weak we start at 5c ) did not work .
I even tried puttimg the heatsink paste on extra thick - but that made it run hotter .

Do you have cool n quiet enabled? It makes a huge difference in temperatures. It won't help you for high load temps though. Make sure the heatsink is fastened tightly and if that doesn't work, check to see if the cpu and heatsink have flat surfaces with the razer blade method. I have the same cpu except i'm using the TRUE. My temps are 57C under load and 32C idle.

The TRUE is machined flat the HR-01 plus is machined concave ( to suit core2 CPUs )
The AMD is flat so when I put the cooler on there is an air pocket right in the middle of the die . I have jus put a TR XP-90C on as a temporary solution and my idle temp is now 34c but the fan on it a Panaflo 92m is far from quiet - and it will have to go back onto the machine that I borrowed it off .
It does look as though I will have to lap the base though - I am just concerned that I might stuff up the cooler doing it !

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I don't believe any HS producer would purposely make a non-flat base. I also doubt that the machinery could be easily adapted to do so.

And the penny/cent/yen/whatever should never go between heatsink and heatspreader! That was simply a trick to increase the mounting pressure and the coin was clamped between the mounting hardware and the upside of the heatsink-base.

I had to lap both the heat spreader and the cooler 42c idle now with the fan running at 500rpm . When checked with a straight edge both were far from flat !

i just thought of the penny because they're mainly made of copper (now zinc or whatever).

rather than just a ruler, sometimes people will use a razor (not a shaving razor, but a straight blade, because they're almost always perfect.