Hi Alex,
I've been interior shopping, too.
Most opinions seem to be that TRF offers the most accurately made interiors. If you'll be getting it too, they make their own carpet kits locally, to keep a lot of control over the manufacture. I think their interior panels and seat kits come from England.
Most of the vendors only stock black, will need to order any other colors and that will mean some time for delivery.
I think VB and Moss get their interiors from the same source. Maybe it's the same as TRF, maybe not. I don't really know for certain.
As suggested, do get color samples, especially if you are trying to closely match original. I say this because my '62 TR4 came with Midnight Blue interior, which is not a common color on the car and quite different from the blue interiors I've seen offered by any of the vendors.
There is a Canadian firm making TR interiors, too. Perhaps they are the source of some of the vendors' kits, but I was under the impression they all got theirs from England. I thought I had the Canadian firm's web site bookmarked, but can't seem to find it right now. Maybe you can locate it through a Google search. I've heard good reports on them, their pricing seems very favorable and they appear to offer some customizing options that aren't available through the "big three".
Have fun shopping!
Alan