They don't seem to have been so profuse this year, Jack. Probably something to do with the 'low intensity' summer weather we've enjoyed. Compared with other parts of the world I think we are very lucky to have the insect population we do, they really aren't anything to bother about. There are tricks you can use to minimise exposure to biting insects, but no semi-wild wetland will ever be totally free of the risk of a bite.

Repellant creams and sprays, quite effective.
Citronella candles and oils, very effective if placed upwind.
Anti-histamine dab-on bite relief sticks, brilliant for instant relief from irritation.

Avoid mooring next to wooded areas and dense ground-growth.
Avoid places where the water is semi-stagnating, such as the fringes of Hickling Broad and the Deep Dykes.
In the highest summer, avoid livestock fields where the Norfolk horse flies have chain saws instead of teeth.

Anchor in the middle of an open broad and you'll avoid most biting insects. In the evening, avoid showing a direct light source to them. It's suggested that the worst type of light is the flourescent tube, because the unit emits a high pitched whistle.

Oh and if Mrs Jack is anti-spider: Conkers!
It is said that spiders hate the aroma of horeschestnut. Bring some fresh conkers and spread them around the boat. If they don't work you can always chuck them at... no I musn't.

But when all is said and done, it's the wild countryside with wild inhabitants. A few simple precautions and they really aren't that much of a bother, they certainly don't compete with the mozzies of middle Scotland which are big enough to conduct a stand-up fight before biting. Even the relatively few wasps around the Broads don't seem as aggressive as elsewhere, the hornets (if you ever see one) are positively chilled-out and really of no danger if you don't threaten them.

Around the Broads you're more likely to be stung in your wallet than anywhere else.

SS