Firstly he owns a mk1 Octavia 1.9 sdi

Alright mate Ian my car keeps cutting out when I'm driving then starts again and cuts out then a can drive it 4 a bit soon when I come 2 a junction put my clutch in it will cut out.and when am driving it a can put my foot down and it won't pick up speed. Any help lol

Air flow mass sensor.

air flow meter

glow plugs

or your intank fuel pump

 

I had the similar prob with my 1.8t would cut out when you start it and wouldn't pick up and wouldn't rev passed 4k when idling turned out to be fuel pump and whoever fitted the induction kit put the airflow meter on backwards, running a lot better now.

Hes not put petrol in it has he

I love the way you re-posted the entire text, including the 'Alright mate' bit...

blocked fuel filter / diesel supply issues

you`re gay?

Definitely not glow plugs they only help initial start up.