The issue I see is that unless you've got billions deposited with the BoE, the interest is (as you mentioned) negligible. Therefore, your only way to pay operating costs is via transaction charges.
Now, private punters don't like transaction charges and can get an account without them from one of the big rip-off artists (who make their money back on selling debt and outrageous "whoops" charges) so they can get a deal which, on the surface, looks better by staying right where they are.
Commercial interests are totally used to transaction charges, of course, but they're not going to deal with you either because... they operate in overdraft because of liquidity measures and tax mitigation. And you can't offer overdrafts if you're operating on a 100% reserve.
The only potential buyer would be the long-term savings market except you can't pay interest because what you earn is effectively nothing.
Shame, but there it is.