All the suppliers do indeed seem to use the original BL part numbers, which I think is a good thing to make sure we get the right part! Often remanufactured or non original parts will have a prefix or suffix to the part number to indicate the fact. Get yourself a BL parts catalogue, it is invaluable for reference.
Supplier websites vary hugely in their complexity (& hence the cost to the supplier in creating & running the site). Trouble is there are literally thousands of parts making up our cars so listing everything is a tall order - not to mention keeping that up to date. I often find that a phone call quoting the part number is a quicker way to find what you want than trawling through large PDF lists. And sometimes the part just isn't on the list - for example Paddocks list for the TR7 is pretty basic but it is well known that they have lots of parts, some quite hard to find. And Fitchetts dont seem to have a website at all but we all know how much stuff they have!
And costs? I think that to some extent we are at the mercy of a near monopoly situation with many of the spares we need, as there is a small number of suppliers who are all going to be aware of what each other is charging for a part. Further, we know that some of the big stock holders often supply parts to the smaller guys, so there is no way that the smaller supplier can undercut on price.
And then of course we are a small market - I doubt there is the volume of trade to allow for much competition on prices. With a slowly dwindling number of 7s & 8s on the road, all the parts suppliers are looking to diversify by supplying parts for other Triumph models, or even other makes altogether. But they have a business to run, & make a living from.
So, get your parts book, make your list of wants/needs, & carry it round all the shows & autojumbles. It is surprising what you can find sometimes!
Tony
<font size="1">1981 2L FHC Cavalry Blue
1980 3.5L V8 DHC Jaguar Regency Red - sadly sold!
TR8 FHC EFI Factory development car Inca Yellow</font id="size1">
