Sounds like the same old story. Do not relax until you have parts in hand. Them telling you the parts are about to go out, means nothing. Last lock set I ordered took 18 months to get, and that was when I was told it would ship 3-4 weeks after the initial order. Finally had to threaten to take the issue up with my credit card company. Parts were shipped within a week of that exchange.
Blackley is the UK version of TRS, along with everything that implies. I don't have a problem with any of the delays and long wait times, it's the dishonesty related to them that is so aggravating. If I'm told the parts won't arrive for 12-18 months, I would be absolutely fine with that, and adjust my schedule accordingly. However, please don't tell me I will have them in a few weeks, and then almost two years later I am still waiting on them, with work backed up because of it.
Like you said though, once you deal with them, you quickly learn how to schedule around what they tell you. Once the parts finally do arrive, you should be happy with them.