Go on, just try it! said the nice lady from Companies House, still patient but sounding a little exasperated.
So I did ... and hey, it works!

No more paper posting and our accounts getting lost because of floods and postal strikes. No more queuing up in the Post Office. No more fear about getting fined for problems I really didn't cause! Rah, rah, rah!
Isn't technology wonderful! And, yes, I did 'phone back to thank her and apologise.