Very helpfull discussion - thank you all.
I will not require to use any pulse dialling equipment
- all my existing phones can use tone dialling (BT Relate 180's from ~1998)
- although I do still own some older antique equipment, but it's no longer in active use.
My current cabling has two seperate cable runs servicing extension sockets (technically star wiring I suppose)
- the shorter run only services a single extension point at the rear of the house
- which is where I might want to install an additional dedicated DSL point
I should be able to isolate one existing wire pair for exlusive use of the extra DSL point
- this would be wired from the DSL AB terminals inside the Master Socket
- and run to a new line box housing twin sockets for BT Phone + RJ11 for DSL
The alternative option would be to run a dedicated CAT5e cable run from the router's location
to a network RJ45 socket at the rear of the house to provide hardwired internet
at that location without moving the router - this might be a better option.