Car has always had this rhythmic gentle judder/wobble/vibration/oscillation at idle since I've owned it (a year) but seems to be worsening.

Usually from cold and until up to temperature this seems to happen on a 3-4 seconds cycle.

The idle is smooth to the ear and I was thinking it could be a worn engine mount as the engine does seem quite easy to rock by hand, why it would largely disappear when the engine is up to temperature is a mystery though.

Presumably the idle may just be that bit smoother when up to temp and the rubber engine mounts damping characteristics change slightly with heat.

Has anyone else experienced this/suggestions?

Bump.

Has nobody else had a similar experience with their engine having a wee wobble or shoogle to itself?

Not in an Octavia. 

 

However I have experienced this in my 1.9 TDI Fabia. It only happens to my car when the weather is very hot and when I am stopped facing up a hill. I have not experienced it for over a year, and when I researched it, I found that some Mk1 Fabia owners suffer from this problem quite badly.

 

The cause is often mysterious to say the least, with most suffers never actually quite getting to the bottom of the cause. Possible causes that I have read about are: worn dog bone engine mount, worn flywheel, timing slightly out.....or a combination of these factors. In my case I suspected an issue with the dog bone engine mount, as it only happens when facing up hill (thus compressing the mount) and when the weather is hot (softening the rubber in the mount).    

 

Perhaps in your case, the easiest and cheapest place to start is the dog bone mount.

Thanks for the input, I'll check things out in due course.