That's not true, sister....
Just because it is a muslim selling it doesn't necessarily mean its halaal. Obviously he/she SHOULD be selling halaal meat but sadly this isn't always true.
And, sister, just by saying bismillah does not make the meat halaal, it would be easier for everyone around of course if this was the case and we wouldn't need organisations such as HMC but this is NOT the case. Saying bismillah is a sunnat act which we do before we eat, yes, but it does not mean that all the food that now passes into our mouths is halaal.
That is why it is necessary for organisations such as HMC to confirm for the muslims here in Britain whether or not our meat is halaal. By halaal I mean that bismillah is said before the slaughtering of the animal, not afterwards when we are ready to eat the meat.
I hope you understand what I am saying. In my town there is only one restaurant that is HMC which does not mean that the other restaurants / take-aways' chicken or meat is haraam but just that it hasn't been checked by HMC so I suppose you could say that it is doubtful.
But the people that are saying that they own a restaurant or take-away or whatever that sells meat, maybe the HMC hasn't got to your area yet, they only started a few years ago, maybe more.
Personally I think the HMC is a great organisation as it is helping the Muslim Ummah......