phoned 0800100444 no. and (almost 15 minutes on hold later) said the key phrase "save on connection" lots - rep lady there was also bemused and has done another order, which should cancel out the other one, if it still stands. phew! what a palava.
Anyway, as I have such a rubbish credit score I have to pay £50 deposit which I'll get back in 6 months if we're good. That's still a lot better than £120!
