I'm not 100% sure, but I think you could have gotten away with deferring the £25 and not paying up front.
I'm with Plusnet and my account details show this charge, but it only comes into effect if I leave within the contract period - so apparently nothing to lose if deferred (I have a new contract as I just moved to FTTC).
That reminds me, don't post often but must update my sig 
For those that think the £25 I had to pay was for line transfer, here is a snap from my a/c page showing PN now charge £25 for activating their broadband.
http://img195.imageshack.us/img195/88/plussnetsetup.jpg As I said earlier, that and caller display charges is the way the cheapies claw some cash back.
I suppose it was a bargain really, as they spent a whole week bu**ering up my line, number & BB!
Edited by deleted (Thu 01-Sep-11 17:00:39)