I agree with Paul, I've always found it preferable by far to keep clients away from editing, it can be disastrous and entail far greater work for yourself of which the client doesn't understand the time taken in reconstruction and subsequent invoice. In fact website design would be a great occuptation if it wasn't for clients

I've looked further into using Google Drive sheets for this and there are some limitations:

* You cannot have a transparent background on the sheet or cells. Shame as this would make life far easier.
* "Publish to Web" doesn't include embedded fonts. Very strange coming from Google.

Good for stirring the old grey matter though.

Latest vesion with padding added:

DEMO