Just doing some final testing on this, and got the concatenation working fine,
The value is passed to Paypal (ECO) successfully, and the product description appears throughout the transaction
However, when the email receipt is sent from Paypal, the description field is empty.
I queried this with Paypal, who stated that "there is no value passed for the product description which caused the missing product information on the email receipt" and i should take it up with Webassist,
The product description is clearly there during the transaction, (I think they are escalating the case) - do you know of any disallowed characters or other reason why the value is not being passed to the receipt ?