I reckon this goes on a lot because the CAA does not send out reminders, and a 5 year cycle is a long time to keep track of.
The German CAA also does NOT send out reminders, ever! First of all, they see it as the pilots responsibility. If it's expired and you still fly, you are doing so illegally in spite of a currant rating. And it IS the responsiblity of instructors or examiners to check that before even flying with you!
Even with the language testing... the German CAA could care less if you have English level 4 or not, it's up to you to get if you want to use the radio in English.
I think the whole licence renewal thing is so messed up since JAA and I wonder some things didn't get straightened up with EASA. 5 years licence, 2 years rating, 3 years instructor, different times for medical, etc. etc.
And also, 12 hours flight time the past 12 months before expire date for renewal. So if you fly 100 hours the first 12 months, they don't count! That is so stupid! In Germany we USED to have 24 hours in the last 24 months, plus at least 3 cross-country flights.... seems a lot more sensible to me.