On Sat, 1 May 2010 07:37:41 +0000 (UTC), Andrew Gabriel wrote:

You would need to make your loft insect-proof to keep them out, and
that's probably not feasable, at least in an older house.

Aye, I found a wsp nest in the loft of my flat once, late in the
season it was *huge* about 18" high and at least a couple of feet
wide. After that I made of point of inspecting the loft in late
spring for the start of nests. If I found any new ones I let loose
with a liberal dose of ordinary household fly killer, that stopped
the nests developing...

--
Cheers
Dave.