If I installed a pump on the hot water outlet from the tank, this would
give
all the taps in the house a huge performance increase. I assume it is
possible to get a pump that is automatically activated by sensing water
flow??

Yes. They are called shower pumps. Stuart Turner are known for quality
versions. Otherwise, cheapies are available. They are quite capable of
running more than just showers.

System is a conventional and vented... OH and can someone answer why it is
that here in the UK these junky (sh*ty) systems are common as opposed to
much better systems on the continent/USA ???

They were banned until the late 1980s. They are widely available now, if you
can persuade a typical Luddite installer to install them. They are usually
known to them as "Heatrays", an anglicised version of "Heatrae Sadia
Megaflo". Most installers think they eat children, or at least shine
ionising microwave radiation into them.

Christian.