I wouldn't even bother going in. Just give them a call. if they give you an outrageous price explain how a moderator on FiatForum bought some for under £300 from a dealer.so what would i do, go in and give them the part number and ask what the damage would be sorta thing?
The standard price for them is over £800. Th reason there are some many places selling them so cheap just now is that they are stock that was lying around with one of Fiats suppliers.
When I got mine the parts guy said if I knew anyone who wanted the same deal to get them to give him a call. So it depends if the guy you deal with is aware of this stock.