Now it's starting to make sense: I didn't realise that the "complimentary" coffee available to first class customers was different to the coffee other passengers pay for. I don't think I've ever had a coffee from the on-board cafe before, as I always get one at Nero or Costa before boarding. That makes me think even less of the service - just how much can a proper coffee cost?
Next time I travel I'll deliberately ask for a coffee before showing my ticket, and then the attendant can choose to give me the decent stuff or pour it away.
They will pour it away (and return the opened item as waste), or charge you for it. They would do the same for tea.
The First Class coffee is not ground coffee, and not advertised as such.
Instructions to avail of complementary items from the buffet are to show the ticket or otherwise identify a requirement for complementary items before ordering, as otherwise you may be charged.
This is because there are different stocks for complementary and saleable stock.
This is nothing to do with cheaper, or a different level of quality, but has to do with stock control and fraud prevention. The coffee machine logs how many cups are made, and this can be (and is) checked against the number of cups put through the till. Same with all other comp items, it's to stop people selling the comps and pocketing the cash.
The instant coffee sachets are also "First Class" or saleable, and also counted accordingly. Saleable coffee on trolleys is the instant variety.
The first-class coffee is usually pre-made in insulated flasks, and has been often changed to attempt to find something that appeals to everybody. At the moment it is not instant, but a new product that is a liquid that is diluted with hot water. Apparently it is a lot more expensive than the granules it is replacing. I can't comment on the taste, I hate coffee.
If you think that the saleable instant should cost less (or indeed, the ground coffee should cost more, as that would be the probable outcome of such a review) feel free to contact Customer services, or bring a flask.
Regarding the sachet being handed over to "do it yourself", I've never heard of that, seen it done, or heard it instructed, the correct pathway is for the CH to make it before handing the coffee over. That might be worth letting customer services know, as somebody needs a swift refresher.