TBH there is no longer any real link with ‘line rental’ , LRS is only available to broadband customers and they don’t have a separate LR and broadband charge on their bill , they simply pay a fee for broadband ‘service’ .
The easiest way to consider this (IMHO) is , for your one off payment of £219.84 , you get 12 ‘credits’ of £19.99 , one per month for 12 months , the monetary value of this is £19.99 x 12 = £239.88 .
Basically the question you to ask yourself , is it worth you giving BT £219.84 upfront for just over a £20 ‘saving’ over a year.(£20.04) , the answer is probably yes, because £219.84 left in the bank would ‘earn’ a few penny’s in interest in a bank or building society current account , certainly no where near £20.04.
In practice the way it works , if your monthly ‘bill’ for service is ( for arguments sake ) £36.00 with LRS ( £219.84 ) paid upfront, the amount taken per month would be £16.01 , without LRS its the full £36, the difference between the two methods over the year is £20.04 saving
