Proc Gmap postcode annotation

[IIIEEE]

I've created my maps using shape files of the UK at  a postcode area level. My proc map import data set has:

X      Y        Postcode-area

-2     56            AB

-2    52              B

-2    53             BB

My response variable is called response from the response_1 dataset

proc gmap map=Post code areas data=response_1;
id Postcode-area;
choro response / ;
run;
quit;

I'm trying to annotate each area with the appropriate postcode-area. 

All the examples I've come across use  %annomac; %centroid, however I can't get it to work for my maps.

Any help will be much appreciated.

Thanks

[GraphGuy]

Here's a simple example that shows the basics:

data my_map; set maps.us;
original_order+1;
run;

proc sort data=my_map out=my_map;
by statecode;
run;

%annomac;
%centroid(my_map, centers, statecode, segonly=1);

data centers; set centers;
xsys='2'; ysys='2'; hsys='3'; when='a';
length function $50;
function='label';
text=trim(left(statecode));
run;

pattern1 v=s c=cornsilk;

proc gmap data=my_map map=my_map anno=centers;
id statecode;
choro segment / levels=1 nolegend;
run;