There's plenty of legit NV on Alibaba. Housings, tubes, lenses, China makes it all now. Assuming you do your due diligence on the seller, I'd have no concerns dropping £2.7 on there. I've done transactions on Alibaba for more...
Just check out the seller. See how long they've been around for. Their rating, transactions. what protections they offer etc. Then make sure exactly what you'll be receiving in terms of spec of the tubes, FOM, SNR, spec sheet included etc.
In terms of cost, in addition to the main cost and shipping, there's a transaction fee on the Alibaba side which I forget how much it is. 2.99% I think. Plus FX fees if you pay by Paypal (make sure to use your bank's rate rather than Paypal's as they make money off you from that). The transaction fee will be displayed before your submit the order anyway. Then import fees, VAT, courier handling fee etc.