Good point, but I am not so sure. Most companies should be able to get their outgoing mobile costs down to 0870 levels.
And I think that I should prefer not to have my mobile number bandied around various companies, at least with the 0870 I have made the contact a little more distant.

I have just looked at the t & c 's of the 25p an hour business plan and found that it only applies to the 'big 4' mobile companies,  '3' and dolphin numbers are excluded.
Out of interest is there a residential version of the 25p business plan for calling mobiles?

As I said before, I don't see a big attraction in getting an 0871 number for revenge.

But I have an 0871 number that diverts to an international mobile at no cost to me (9p/min from BT), and also an 0844 number (like bigjohn's Paypal number) that also gets there via an American 760 area code; 2p to the caller, 7p to me, or a bit more if I change the routing. My O2 mobile can then divert to that 0844 from inclusive minutes.

So I don't feel like the hypocrite mentioned; I think that these numbers are very useful for better reasons.