They’re very different. The BBC is an independent organization funded directly by license fees paid by television owners. Unlike RT, it is independent from direct government intervention, and it doesn’t attempt to advance the interests whichever party is in power. The BBC primarily exists to serve people living in Britain. RT is directly funded by the Russian government, and is targeted primarily at other countries outside Russia.

In the context of a nation the UK had an adversarial relationship with, yes, that would be a prudent thing to point out.

I guess that depends on how much you trust a government news source when that government is headed by a guy that murders journalists that disagree with him.