We're told that we need to have our rental property inspected to comply
with H&SE requirements and that it will cost £81 every two years for the
privilege.

The property is a 2-bed modern terraced house with a combi boiler. If
the CH system was installed following the manufacturer's guidelines and
is delivering hot water to the taps and shower, I don't see why an
expert inspection is required periodically. At most, a once-off
inspection of the installation should suffice, with periodic checking
that water is hot at the taps and shower[1].

Here's what the H&SE advises:
http://www.hse.gov.uk/legionnaires/what-you-must-do.htm

I can understand the need to take such measures for large premises -
office block, hotel, factory etc. - but OTT otherwise. It looks like an
opportunity to make easy money for those doing these inspections in most
other cases.

I'd be interested to hear the opinions of others on this.

[1] We do regular general inspections of the property anyway, but tenant
would soon complain if the shower ran cooler than normal in any case.