There are a few different considerations here, what is the item worth? From memory you have a fairly low limit on what would not attract duty (~£30 or so but I'm happy to be corrected here) so if it is under that then it should be fine in terms of extra charges.
If it will be shipped to your home safely depends on the seller, his packaging and the vagaries of both the domestic and international postal services.
I don't believe you would pay VAT as such, you'd pay duty on it which amounts to the same thing in effect.
Finally, yeah you could just purchase it and see what happens, it might or might not get stopped depending on the value anyway.