I think only Wiggle can answer your question. If it's not a brand name saddle, and is not being sold separately you won't be able to replace it with exactly the same one. Saddles that come with bikes are usually not top quality, even though sometimes they can be comfortable. I would pick a mid range saddle of similar shape and go with that.

I would take the bike to the mechanic to look over and see if there's any more damage. If there is, ask for a written note listing damages and estimated price of repair/replacement.