Glad to see Steamjuice is already on your list of custards to try. I'm a big supporter of them / their e-juice. Although I would highly recommend you request they add extra flavor in the comments section if / when you go to place your order, as the only knock I've heard against Steam is that some of their flavors are a bit too subtle (mute) for some. I've asked for extra flavor on every e-juice I've ordered and have yet to be disappointed.
Also, and it's been said already, but I would certainly add ITC to the list.
Lastly, and they may not qualify since they don't offer 120ml+ bottles, nor are they typically cheap... but NT's Custard's Last Stand is a must-try -- especially with their current BOGO 50%-off deal.
I couldn't get into the Thick Vanilla Custard from Steam Juice. It was definitely too subtle and not very creamy for me. It wasn't horrible but I wouldn't re-order. Jerry Juice on the other hand... I see a 120ml jug of that in my future.
I agree that Custard's Last Stand is definitely worth trying. I just had to let it sit for a looooong time before the flavor hit its stride. Don't even remember how long I left it on the shelf. I kind of forgot about it and saw the bottle one day and though "Lemme try this again." Very tasty. vaping some of the Absolut Creme Brulee right now. Also very tasty.