No - BR didn't really "preserve" anything.
The 2BIL you cited was a member of the National Collection when it was running in the 80s.
The 306 was part of the National Collection and on loan when being run in the 80s.
The 4SUB is just about the only thing you could argue BR "preserved".
BR didn't "preserve" anything else - they repainted a couple of units in a retro livery. Nothing more. The 4EPB you keep banging on about being a case in point - it was withdrawn with the rest of the surviving 4EPBs in 1995, until that point it was an operational EMU, not preserved in any way, shape or form.
People aren't "rubbishing" BR achievements - they're rubbishing your argument that BR "achieved" something in this space where the facts really don't support your argument. But as ever you're doing your normal trick of either denying reality or shifting the goalposts to suit your argument.
This really is getting tiresome.
Here's the starting point and the end of my argument. There were various electric units which one could travel on on the national network during the 1980's and 1990's at special events that were clearly heritage in nature. That is a matter of historical fact. With possibly the exception of the GE unit, that has not been the case since then during the privatised era. I regard that as a step backwards.
I point out this reality then I get some drivel about how I'm banging on about my preferred SR type units.
In response I point out that actually there were units from other regions around at the time, then I get another load of drivel about how BR at the time was supposedly rubbish at running and maining these units, because they didn't actually preserve every single type of first generation unit that existed.
I point out that it was good going to have had the heritage units that existed, and now apparently even though these units were maintained and looked after by BR's teams so that they could go out on the network, this still supposedly wasn't an achievement because the NRM owned some of them (something I've already pointed out on this thread BTW).
As for EPB 5001, 1995 was when the network was in the throes of privatisation. Who's to say that it might not have remained with the 4SUB and the others somewhere under the old regime.