Fair question, PLOC, or prolonged loss of comm's is relatively common for any number of reasons.
TX Rx going to sleep is one problem on the Boeing Types, controllers are generally aware that communicating with atc is only one of the demands on a pilots time.
You know the saying: things tend not to go wrong in ones and twos.
Admittedly when approaching an FIR boundary one should be aware of the required freq change.
But approaching London, one of the pilots is totally involved with getting in touch with ops, handling, engineering and getting Wx.
Hope that helps.
P.S London is great, undoubtedly the one of the very best in the world! Particularly those whom wave the height and speed restrictions when available
