Although this might sound trite, I have never heard a bad word said about any of the dealers who advertise on this forum.
I have personally bought from Red Dot more than three times, and there isn't a straighter dealer around. The coffee is good too.
The same can't be said for all London dealers.
At the end of the day, there's nothing to beat developing a relationship with someone you trust. If it's a local guy and you can see the whites of his eyes, then so much the better, but if they are remote, and accessed via the phone or 'net, then that's OK too. Provided you know what you are doing.
Personally, I am very much in favour of picking up the thing that you are considering spending your children's inheritance on, in your own hands. Nothing beats playing with a toy before you buy it. Buying remotely is always fraught with dangers, and having had my fingers burned once, I no longer do so.