So, all of the items (other than the one that was now flagged as out of stock) arrived on Friday. That was a month from order to dispatch for items that were listed in stock.
The item that is now out of stock (despite being listed in stock when I ordered) has no update other than they were expecting stock in late-May.
This will be the first and last time I use Tweeks for sure. I liked the idea of getting most of the components from one place, but in future I'll just buy items separately from the likes of CRC, Merlin, Tredz, Planet X, etc.