I did my PPL in 2000/2001 and notams were not covered.
In 2003 I busted a French power station TRA when the stuff was not in the (then just barely usable) internet notam briefing system (ais.org.uk).
And I am pretty savvy when it comes to internet use, including mobile internet. I've had mobile internet since
this trip in 2003.
It is a safe bet that no pilot who got his PPL more than 10 years ago (90% of the UK PPL community?) has been trained to get notams, and a large % of those trained more recently don't bother.