Not sure where you get the idea that "the BGS don't even bother to take their own measurements" and people don't bother to check the BGS website. I have always looked at their site after previous quakes.
The BGS have a network around monitoring sites around the country. I would think the data from them is fed into a worldwide network and probably used by the USGS.
"The BGS operates seismic instrumentation at over 140 sites in the UK. The majority of these sites is equipped with either vertical component or three component short period seismometers. To record large earthquakes on scale, accelerograph stations are installed at more than 25 sites. In addition, a number of broadband stations are installed, providing data over a wider frequency band."