Well Tommasini's are rare and desirable so it could fetch good money. The veloce groupset however is only an entry level group and it looks as though it has Shimano (Ultegra?) brakes on it and possibly a dura ace rear mech.
I've not really an idea of the value, as I said above I'm no expert, but I'd be disappointed with less than £500 for it and would hope to get about £600. The only other one I could find on the net was a very nice spec model that went for a grand earlier this year.
Perhaps your best bet would be to put it on Ebay as a 100% charity auction as I don't think they charge any listing fee or commission when you select this option. Alternatively put it on here in the for sale section for £600 and see what the response is, if I have got the valuation very wrong I'm sure someone will let you know, they're a good honest bunch on here...mostly
Hope that helps. Perhaps someone else can ratify or correct what I have said?