With stalking, because you need expanding bullet heads you can't get them via the post as it has to be face to face and entered on your FAC. You can get the other components without showing your FAC at all.
In practice for the stalker this means finding a local supplier.
Henry Krank in Yorkshire does cheap 143 - £42 for 100, or you can pay £123 per 100 for supposed 'better quality' stuff elsewhere. But they need to send the expanding stuff to your local Registered Firearms Dealer (unless they have it in stock) for you to collect, and they will charge you for the service.
A lot people reload, it's a bit cheaper in the long run with things like 243, not as much with 223, and, as you know Rene, that's the way you can have most faith in your ammunition.
You can buy non expanding heads without even having a FAC ( AFAIK). But the law in the UK says you HAVE to use expanding ammunition when shooting deer. So a lot of people end up buying whatever heads/powder their local supplier has, work up a good round, then buy as much of the same as they can and stick with it.
Many people end up changing loads because they can find their usual powder/heads.
In practice you'll find enough RFDs near you get what you need unless you are doing something exotic.