|As long as the CD you choose to use has the same style/type of "key" that you already have.... then there ought to be no problem...|
You cannot use an OEM disk with a retail version key; and likewise an OEM key with a retail disk...
Incidentally you mention the version you bought an age ago cost over £100.., which suggests you're in the UK: whereabouts?
As you apparently have a legit key... have you also contacted M$ to see if they will replace the disk. Just tell them it got damaged - as in cracked/broken... and see if they will oblige (possibly for a few pennies)?