Thanks Eddie!
Its a bit of a difficult one...initially I had thought about setting up a "downloadable product", so the user pays for the file, and prints it off themselves. Not going to work as I'd need to add a voucher code, it would have to be the same voucher code, and then there's nothing stopping repeated usage without actually having been paid for.
Then I thought, set the downloadable file to have the instructions of what will happen in it....I would then set up a unique voucher code and email it to them, and they could print it off themselves...but then that looks a bit shite when handing over the voucher to a person on their birthday or Christmas.

Thinking the only way to do it properly is to physically post vouchers to the purchaser. I would hand write in the voucher value, and code to be used when making a purchase on the site and leave a space for the buyer to enter the receiver's name themselves.

Needs a bit more thought as how best to do it....hmmm!!