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.