Hello
The mdf code is a code that has not geographical use at all, its a building ID code.
The postcode is a UK spec postcode and can be geocoded.
Looking at the tool you have provided only Yahoo get 3 sample postcodes correct, map quest fails every time. Google gets the locations very wrong.
Also in my spreadsheet the postcodes are in the format of S753JL this fails, but if I edit the postcode to S75 3JL the geocode from Yahoo is correct.
I now have to edit 2,500 rows of data. doh!
Thanks for your help