The new X is better, but not $50K better, no way not even close. If your lucky enough to have a bank account which can absorb $50K without worry than its a no brainer to get the new X. But us 60D owners aren't in the same ball park/mind set, otherwise we wouldn't have got a 60D in the first place .
The Y will offer the extra space the 3 doesn't, and come in ALOT cheaper than a new X, that's what we are waiting on to replace my wife car.
The economics in the US may work better due to incentives, I am for sure no expert on how to arbitrage in the UK.
Regarding the Y though - I would not put high hopes on it as an X replacement.
It's more storage than the 3, but not close to S/X caliber.
The 3rd row works for Minime, Tyrion and little children.
I sat in it and paid attention to when the people were exiting the car, the humans were of smaller stature from the rear row.
I too had a 60D.. with cloth seats. and white paint when it was free.
I had to leave the 60D club though once upgrade dropped to $4,500. I was tired of seeing "you must slow down to make it to the supercharger messages".