As I know you were all wondering what happened next

here you are:
After about 3 days, the phone line was working beautifully with no crackles, but now the internet/broadband connection was totally out
So I phoned the helpline again, told them we had received the new splitter but still no connection, so they said they'd send out an engineer on Saturday. He duly arrived (early !)and confirmed the connection was dead, then proceeded to plug in various bits of his own equipment, which worked. He then re-connected our bits, and hey presto - connection. Unfortunately he had no idea why what he had done had worked, so there's no saying it won't happen again
What did shock me was that if he had had to replace anything (including the router which was provided by the company in the first place !), then we would have had to pay for the equipment & a callout charge

. However, as he had not found a fault, there would be no charge, which while I am pleased, seems ar$e about face to me
