I only just picked up on thius thread!
I agree with the above: I have an old plugin phone (normally on a shelf with its cable wrapped round it ... ) for this kind of situation! I've never had the phone line dead during a power cut.
On the general theme of the thread: In the regional telephone directory ("businesses and services" section) there is a 1/2-page entry "EDF ENERGY" (pointed to under "Electricity") which gives the number (0800 xxx xxx, so free) for reporting faults.
When there have been power cuts I have called this number. The initial interaction is automated, and in the course of this you get a recorded message on the lines of "We are aware of a fault in the X-Y-Z area. Our engineers are working to fix the fault and we expect the power to be restored by XXpm". The time is rarely more than an hour or two out!
By the way -- I too am on the end of a power line which arrives overhead across the adjacent river, then plunges underground in the farmer's field at the back of the houses. The cable once got ploughed up! Big bang, but nobody hurt. Out for over 24 hours.
Best wishes to all!