transmission banging

[Nicholas Lewin]

I have my lovely 240 estate back as of today and she is stopping much better than she was - thank gawd for that!

But, you know what, there's still some grumbling going on under the floor...

Here's the history as brief as I can:
1 Bought at 98k miles - transmission smooth as you like in all aspects except a weird vibration in top gear 45-60mph. No clutch judder and no banging
2 2nd hand g/box fitted and clutch changed. Much vibration. Undriveable
3 f/wheel skimmed (allegedly burned). Better but still bangy
4 use car. Banging gets better
5 original g/box vibration investigated - turns out to be shagged main shaft/top gear - so a genuine fault (but no longer relevant)
6 car still banging (low speeds - especially reversing)
7 s/h (111k mile) propshaft fitted. Better but still bangy

So what's the deal? It's had new suspension bushes all round (3 months ago). The clutch itself new 18 months ago

Possible centre bearing on prop? Possibly still the flywheel being a bit rough?

Any thoughts folks?