And you're confident that you can tell the difference between wasps and
honey bees?

Yup.... Having had my hands in many a bee hive, I think I can recognise them
by now ;-)

'Cos it strikes me that if some folks are already killing what
they believe to be wasps, then they might actually be killing beneficial
pollinators - rather daft for gardeners.

Absolutely. However, wasps are also *good* for the garden, cleaning up plant
pests such as aphids as well as dead wood, and plant matter. So why kill any
of them if they aren't harming us?

Can any wasp experts say if wasps have much need for water at present?

Well, according to www.jungleformula.co.uk, the people who do the
anti-midge/wasp stuff, wasps in the UK are out looking for water, meat and
wood pulp from April to mid August.

Best,

- h