interesting link oilman.
I used to work for a woodworm treatment company (years ago) and it was well known that the whole process was largely a waste of money, praying on the fears of people for thier property.
The thinking went something like this:
At best the solvent based chemicals only penetrate the wood to a mm or so.
The adult lays its eggs/larvae, thousands of them, into the wood through an ovipositor (a syringe like tube) below the chemical layer - so no harm is done by the chemicals there.
The grubs spend years (up to five years) munching away through the wood below the chemical layer - no harm done to the woodworm there either.
when it matures the woodworm emerges to mate, in doing so it eats approx 1 mm of sprayed wood (if it is unlucky enough to find a bit you didnt miss) and dies (or with some chemicals becomes infertile).
out of the many hundreds that survive to emerge from the wood only a small proportion are killed (unless of course you sprayed absolutely every surface of every piece of wood, including beneath paint and exposed flooring surfaces - in other words dismantled and stripped all the wood from your house prior to spraying).
The survivors mate and return, each to lay thousands of larvae. and the cycle begins again.
At best spraying could only minimise damage for future infestation, the five year munch cycle will carry on unaffected.
the reason that all wood in houses isn't completely eaten away by woodworm is, as the link suggests they stop when theyve eaten the tasty bit, which is comparatively small sections of most beams, boards and panels. this is why woodworm companies love to offer 30, 40 or 50 year guarantees.
save your money and effort and just replace any structural threat.
Even the dreaded death watch beetle would only threaten a building if you are concerned about its stability for the next 300 years, if so - what are you doing using galvanised joist hangers, plasterboard, gripfill etc.
Now termites thats another matter.
Boxcleva judging by the photos JohnD may have a point about rot - the filaments in the photo could be early stage dry rot, but on the other hand they could well be a light covering of spiders web also.
try rolling some up between your fingers, if its spiders web it'll compact into a tight hard little ball, if its dry rot mycelium it'll sqidge into nothingness.
If it is dry rot the best cure is to remove all you can and ventilate the location well - dry rot cannot survive in a well ventilated area, you could try lightly burning the surface with a plumbers blowlamp to kill the existing rot (if that is what you have) but the risk of fire should be considered, especially around the tinder like insect damage.
Chemicals are equally suspect for killing dry rot, although household bleach does a very good job. the household fear industry is good at thinking up ways to part you from your money.
The wood boring insect damage does look to be quite aged, personally I would replace any overly damaged bits and forget about it - well maybe id take another look in a couple of years to see if anything has changed.
good luck
Am i looking at a possible infestation of some sort ? I havent noticed any other obvious damage to any other wood in the house . 
