Yeap, BES is often my first call.
eBay. Aliexpress doesn't fill me with confidence in the same way as eBay but I have used them with no bother. Context Pneumatics, I probably find them more useful because I don't do things like many folk here, via eBay (for few offs - postage included in price) or direct (for bigger orders, one postage charge covers everything, but that charge is steep for just a few things).
On the subject of valves: the three piece valves are probably full-bore, the one piece valves are probably restricted bore (not what you want), and the two-piece valves are a lottery, if they are cheap and don't say they are probably restricted bore (time to play safe and go to BES who state one or the other). Why is restricted bore bad? A. You spend all that money on large bore pipework and then limit its value with a restricted bore valve/tap - bit cuckoo that.