I've to blakemars quite a few times. When I've been working nearby & popped in, as well as going along with the London pipe club boys.
Mike (the owner/pipemaker) is an absolute gentleman. Always got time to down tools, & listen to your wants & preferences. You want to come along with the pipe club, as they take the whole workshop over! Food & drinks laid on, & it's a very enjoyable & interesting day.
I've never been to invicta briars place, but I have met him a few times at the CLA game fair at bleinham palace. He always has a stand there selling his pipes & tobacco.
Hope this helps, Simon.