Called into a dealer today, the problem stumped them. Awaiting their discussions with Subaru UKHO now. They are experienced Subaru dealer and this anomaly seems to have caught them on the hop. I agree Pete it is a bit silly that that an hijacker creeping up on the nearside can still get in.
However, having studied the manual further I discovered that the ever searching fob can be put to sleep easily to save its battery life, and it works OK. No need for a Faraday box in the kitchen. (The dealer didn't know about that until I showed him, in the good books for future service costs now🤣)