I wish to install a sky digibox, but do not wish to run cabling for a
new telephone extension.  Is there such a thing as a wireless
telephone jack that will work in the UK?  I've seen them advertised in
the US.

The Thomson Wireless Phone Socket has been used successfully with Sky
digiboxes, and is available online at:

http://www.buyitoverthenet.com/

(It's near the bottom-right of the main page. For some reason, their
site won't allow deep linking.)

According to http://www.phonex.com/where.shtml , you may also be able
to find a wireless phone jack under the "Phonex Broadband" or
"EasyJack" brand at PC World, The Link, or Suzo.

Fantastic, I've been looking for a service such as this for ages. 
Excellent answers and comments, I now have just what I need.

Yes, Challange-TV http://www.challenge-tv.co.uk/ is based in Kent and
normally stocks Wireless Phone Jacks. However as you'll find the
Thompson Wireless Phone Jack is currently unavailable. I would suggest
giving them a call.

James

PC world sell them

If you have a DECT compatible phone system you can use the "BT Diverse
Cordless Socket" which operates like a normal handset. Unfortunately
they are also rare and cost £80 if you can find them now. The seller
"commswholesale" on eBay told me they ocassionally have them in second
hand.

Finally, if it is an installation by a Sky engineer you can run a
temporary extension for them using a wind-up reel and then unplug it
and wind it up again when they have gone :-)

Gareth