I've seen the off-peak (Mon to Fri nights, and all weekend) account from
Claranet <http://www.uk.clara.net/homeaccess/broadband/offpeak-main.php>
but would like to know if anyone has run speed tests on this, please.

Looks useful to me, or anyone whose usage is not daytime, and at a 
moderate price, too.  Views from Clara users welcome.