thanks to all the constructive info
instead of replying to you all individually, i started this new thread.

husband home
heres what hes done so far

the first controller is an 'ACL lifestyle model LP522'
ACTUALLY FLSHED OUT WHEN FIRST NEW FUSE WAS PUT IN
it was then replaced with 'Siemens RWB 9'
WHEN FIRST FUSE PUT IN IT WORKED,THIS WAS ABOUT A MONTH AGO.
OBVIOUSLEY DUE TO THE 'HOT WEATHER' THE HEATING HAS NOT BEEN USED MUCH,
AND OUR HOT WATER IS SUPPLIED BY EITHER IMMERSION OR GAS AND IT WASN'T
NOTICED UNTIL A FORTNIGHT LATER, THAT THE CONTROL BOX WASN'T WORKING
AGAIN
I DISCONNECTED THE PUMP, FROM THE SYSTEM AND STILL THE FUSE BLEW
RECONNECTED THE PUMP AND DISCONNECTED THE VALVE,STILL THE FUSE BLEW,
GOT THE HOT WATER TO FIRE,THE PUMP WAS RUNNING OK,SMOOTH AND USUAL,
WHEN THE HEATING WAS TURNED ON,THE FUSE BLEW AGAIN,
I DISMANTALLED THE MOTOR UNIT ON THE VALVE,SO THE VALVE COULD BE
SHIFTED MANUALLY,GOT THE HT WATER FIRED AGAIN, MANUALLY SHIFTED THE
VALVE,AND GOT THE HOT WATER TO RUN THE HEATING SYSTEM,AS I WAS TOLD
THERE COULD HAVE BEEN POSSIBLY AN AIRLOCK CAUSING THE PUMP TO STALL,
BUT DOING THIS PROOVED THERE WAS NO AIRLOCK IN THE SYSTEM,
WITH THE VALVE STILL SWITCHED TO CENTRAL HEATING SIDE I TRIED TO FIRE
THE CENTRAL HEATING ON THE CONTROL BOX, AND THE FUSE BLEW AGAIN,
THE NEXT THING I DID WAS TO DISCONNECT THE THERMOSTAT,TRIED IT AGAIN,
AND THE FUSE BLEW AGAIN,
THE BACK PLATE HAS BEEN CHANGED ON THE CONTROL BOX,STILL BLEW THE FUSE,
THEN THE FUSE WAS BLOWING WITH ALL SWITCHED OFF ON THE CONTROL BOX,
PURCHASED ANOTHER CONTROL BOX,STILL BLOWING FUSES

SO THANKS PEOPLE FOR ALL THE GREAT INFO SO FAR, IF THIS HAS ENLIGHTENED
ANY OF YOU FURTHER
WE WOULD APPRICIATE ANY FURTHER ASSISTANCE
JO