Grafter, those fuel cells look like some sort of moulded plastic. What foam is enclosed in the cell? Use the wrong foam for the fuel used and it can break down/melt and clog up any fuel filters. Bottom mounted outlets are not ideal; any problem with fuel line or outlet and the whole tank will drain without any other form of cut off. Top mounted take off and breather must surely be safer? Are the company Aerospace/FIA/MoD accredited?
Take the quoted price, add on freight charges, add on import duty, VAT and clearance charges, then get an ally or steel tank made to suit; what's the total so far? I bet it wouldn't be too much cheaper than what I quoted.