I've had the same experience, BT engineers perfectly happy with my 'tampering': even suggested a few changes I could think about. I had to repair the installation after the last visit (swop A and B wires). Only had them out twice in 10 years so not an exhaustive sample I agree. Have had similar understanding service from the overhead electrical supply engineers, though I don't think they knew it was my tree-lopping activities which (may or may not have) caused the pole to break............
