Beside the documentation that The OU provides I have found very useful the following tools available on the Internet.
Calculator
http://cleveret.net
I find it very useful to make module result combinations and to know which is the worst and best case scenario for me, etc. It contains useful Manchester google maps for the metrolink as well.
Handy PDF Table
http://open.wibble.to/hons_class_table.pdf
I find it very helpful as being so graphical it helps to see the relationships between the possible combinations very fast, there are a lot of more resources in the main page, they are mainly for old modules but can have some use for someone.
Be aware that some degrees have some modules that mandatorily will appear as part of your degree calculation and others that even being at level 2 or 3 will not count at all for it.
Hope you find it as helpful as I did.
NOTE: These tools are related with the way The OU degree classification calculation is done and not for other Universities, they are not developed by The Open University else by former or current pupils and of course you can only take it as an approximation to the degree you can expect. No exact science here.
