or is there sometimes a delay between my turning the key and the engine turning over?

Could be the same as my Mk3 Octavia, if the glow plug light is still on the dash the engine won't crank.

As Moley said. If you turn the key or hold the Kesey button in as soon as the light goes out the engine will start. Obviously diesels only.

Edited 12 March, 201610 yr by Danny 57

We found that we can turn the key and let go, and the car will start when it's ready - obviously with brake on all the time. This is more noticable when it's really cold outside.

do i have glow plugs?

If you have a diesel engine then yes. They're heating the engine while the orange light showing a coil/spring shape is lit up. In the UK/Irish climate it's possible to get away without glow plugs if the weather stays over feezing.

or is there sometimes a delay between my turning the key and the engine turning over?

You must have the same imagination as me then. I too, have a delay.

Edited 14 March, 201610 yr by kevberlin

I thought Di engines didnt need glowplugs whereas iDi did

the old Transit 2.5di Banana (possibly the best diesel engine in the world) only had glow plugs as an option

I think there is a ECU check carried out when you turn the key (the speedometer and rev counter needles do a sweep) the engine won't start until this is completed.