Spot on Barge Captain 111k miles.
Lot of motorway miles but I think the previous owner drove it hard (from what his wife said when he was selling it!!).
I've made a bit of progress on this and (of course) it agrees with Mark's diagnosis.
I'm now fairly certain it's clutch drag. Basically the higher the revs the harder it is to change gear. If you let the revs drop to below 1k it pretty much changes fine (whatever gear, whatever speed).
Had a chat with the local gearbox centre today (very nice chap and very helpful). He thinks my symptoms aren't gearbox, they're clutch. He suggests taking it all apart and having a look (easy for him to say!).
He did say, though, that the dual mass flywheel can become a bit soggy and follow the friction plate a little, causing drag (very expensive).
Got the prices from Vx today:
Clutch kit 93185904 Trade Club £169.76 + VAT
Slave cylinder 9126743 Trade £161.53 + VAT
So this isn't going to be cheap.
A dual mass flywheel OEM seems to be be about £350 + VAT. I believe the genuine part is £900.
Now what do I get?? Or do I take it apart and have a look first??