I have to ask one question though. Why are you getting it made in China and not the UK? It might be worth going to a small local fabricators and asking them how much it would be to knock a sample up for you. If you do the design work it can work out pretty cheap and if you can put an order in for 50 then you have a good haggling position. You can then also go back to them when you have designed some concials. They should also be able to weld some pipe stubs onto the bottom for the drain so that there is no chance that it can leak from there and it will mean zero deadspace if used with a false bottom. My experience with chinese made products is not very good. At least if they are local you can go and see them. Also saves a lot of hassle with regards shipping and customs. You also save some money by clever design as the outside does not have to be welded as it is not coming into contact with the liquid and could be rivetted instead.