AVB Engine - Vibration

[JFB5Estate]

I have 2005 Passat estate, 1.9 TDI AVB Engine, 140k miles, owned since new.
It's not pretty, with the common wing rot and some err car park re-modelling, but it's been totally reliable, and I've looked after the engine (twice yearly oil changes) and never thrashed it.
It has developed a very annoying vibration, which you can feel through the drivers seat at the 800 rpm idle .
At first I thought it was just the RH headlight, which I could see moving, and if I pressed on it with my hand I could feel the vibration (in the wing) reduce. I now have some inner tube jammed in to stop the headlight dancing about, but inside the cabin it's not really any better.
At about 120k miles, I had the all the front end belts, crank shaft pulley, tensioners, alternator clutch pulley etc done, so it's none of that, and one of the engine mounts (leaking) was replaced at about 130k.
As well as the idle vibration, it really bangs away if you pull up hill at 1300-1500 rpm, then magically above 1600 the vibration disappears.
In contrast, when stationary and in neutral , there's no vibration in the 1300-1500 rpm range.
It's so annoying, I've taken to switching off the engine when stuck in traffic.
I'd like to keep the car going for a bit longer so my boys can learn to drive, but it's not ideal in its current state.
What's likely to be the problem?
The other engine mounts , subframe mounts , drive shafts ?
Any advice gratefully received.