SRAM have stated repeatedly that they will not accept warranty claims on grey imports. They absolutely can trace the origin of all parts via serial numbers. As above though, your contract is with the retailer and if it’s faulty, they are liable to put it right.
Things get trickier if you have a problem more than six months after purchase as it’s then up to you to prove it was faulty, rather than the retailer to prove otherwise.
I would base my decision on whether I thought that the retailer would look after any problems in the absence of support from SRAM and whether you think that you could prove the product was faulty if it developed problems down the line.
How good a deal is it compared with what you could negotiate with a retailer selling an official UK product with bleed kit etc, and SRAM warranty?