There are quite a few speedtesters you can use -

Zen Internet - Test Files
http://www.speedtest.bbmax.co.uk
http://www.adslguide.org/tools/spee..
http://www.lucidni.com/speedtest.ph..
Andrews & Arnold Ltd - Broadband speed test
http://speedcheck.ispconnect.co.uk
http://www.dslzoneuk.net/speedtest...
http://specials.zdnet.co.uk/misc/ba..
SkyUser is the best ofcourse