1500, cutting out, stalling, making me cry

Hiya peoples, hoping theres a light at the end of the tunnel
I have a 1500 mk1 that has had a new head gasket, fuel pump, coil, dizzy cap, points etc, which runs fine for approx. 10/20 mins, then under acceleration it will judder and jolt, the throttle pedal has no effect and the car stops and refuses to start for sometime, maybe itll run for 5 seconds then die again.  Sometimes it will be running at 50/60mph and then misfire once or twice then gradually get worse, until again, it cuts out and wont start.
Has anyone had any similar problems?
Thanks people
Richy

Fuel filter injectors fuel lines? Rusty filler? May be full of rust?

could be carb icing, check warm air feed pipe is there, metal shroud on exhaust hasnt fallen off, both vac lines to temp sensor are hooked up and finally the warm air diverter flap actually opens when engine is started