Certain types of orders will contain the RID of the gaining provider - Reseller identification (RID) codes Reseller identification codes (RIDs) are a type of code that Ofcom allocates to communications providers (CPs) for administrative purposes. They are three-character alphabetic codes which are used in the Notification of Transfer (NoT) switching process and can be used it identify a reseller of wholesale services.
So in the OP father's case the gaining providers identity would probably be known by BT retail (the losing provider) since the intended transfer of the line to JL (the gaining provider) are both providers of BT wholesale (BTw) services.
Indeed, makes me wonder why there has been such a mess of it for what should have been something so simple. Nearly a month from order to the newly promised activation date and no phone for 24 hours. Ridiculous, really.
Well here we are one month after he ordered an ADSL service and he's still not been connected and still hasn't been given a firm date for when it will be activated. John Lewis/Plusnet have had his line for at least a couple of weeks now so what on earth is making it take so long?
This should have been a simple switch from one BTW provider to another.