downsman wrote on Oct 14^th, 2007 at 5:59pm:

Rates depend on what provider calls are made with.

There is a page on this at the top of the 'Chat' section: Geographical (01/02) Vs 0845/0870 price comparison 

downsman wrote on Oct 14^th, 2007 at 6:23pm:

The rates are listed:

Dave wrote on Jan 10^th, 2007 at 1:16pm:

In answer to your original question, BT and Talk Talk have done away with weekend rates for 0845/0870 and most mobiles. Daytime and evening rates now apply seven days a week. 0844, 0871, 09 and other numbers remain unchanged, ie they still are charged by daytime/evening/weekend time periods.

The changes that will happen on 1 February 2008 will be that 0870 will become the same rate as a 01/02 call, or that is the plan.

Note that the "Specialised Numbers" bookllet from BT linked to above and in the comparison page is now out of date. It was published in March and so still shows the old rates. Call rates are correct from the BT Price List. Links to the relevant sections are on the comparison table.