I wouldn't worry...
I used to work at Bosch (who supply parts for the vw common rail diesel engines), and heard a rumour that there was a global shortage of 1.8 20v NA engines due to their extensive use in other VAG models ( Audi A3, VW Passat etc ).
Other people have said that the 1.8 20v NA engines weren't popular due to their high-revving nature (i.e. you have to boot it to get it to move rapidly), and replaced it in golfs in favour of the 2.0 8v, which picks up at lower revs (despite it being about 1 second slower 0-60!)
Rich