Yes we have grey market gear over here in Ireland, but the lens from eglobal central comes with a two year warranty.
It comes with a two-year warranty backed by eGlobal...
Not Sigma.
And therein lies the rub with grey market kit: warranty support and, in a broader context, support in general. For example, eGlobal can't repair your lens and Sigma won't. It comes down to whether you trust the vendor to back your product both during and after the warranty period since the warranty is only as good as the company behind it.
Some people find this warranty/repair arrangement acceptable, others do not.
EDIT: Apparently in the UK the standard Sigma warranty is two years, which is extended to three years if you register the lens.
Per Sigma:
You’d expect the world’s number one independent lens designer and manufacturer to offer you something extra, and that’s just what we’ve done - extending the traditional one year European Warranty of our world class lenses by two years free of charge, to provide Sigma UK customers with an unrivalled three years of cover in the UK. Before purchasing your Sigma lens, please check with your retailer that the lens has been imported by Sigma Imaging (UK) Ltd. If the lens has not been imported by us, the extended UK warranty will not be available.
And that's where the savings come from when buying grey market kit. It's a bit of gamble, as I see it... You're betting nothing will go wrong with the lens, or if it does, that the vendor will exchange it in a hopefully painless transaction; against paying for a full manufacturers warranty that insures you have repair support for the life of the lens because you're betting something will go wrong with the lens. During the warranty period your repair, most likely will be free. After the warranty period you'll be charged for repairs. With grey market kit Sigma will NOT repair the lens at any time, for any reason, even if you're willing to pay for it.