Problem solved. 
  
I decided the only answer was to enter all the possible combinations from 1 to 9999. 
  
There is no zero, so that must eliminate some numbers. 
  
Then I thought just maybe only one of the default digits were changed. 
  
So I entered 1111 
2111 
3111 
etc. 
  
1211 
1311 
1411 
etc, 
  
and so on 
  
until I reached 1131 and got back in, phew!!!! 
  
Hope this may help someone else. 
  
I have reset password to 1111 and will be writing down the final one I use. 
  
One happy chappy. I have spent many hours on this.