Mike,
Sorry to hear of your troubles here, I'd certainly say it's a rare case for a 1.8 VAG lump to suffer in this way; Audi has built 1.8T units for years and years so are reputed to be one of the best in my opinion..
The only thing I can relate this to is my first car, a 1.8 8v Vauxhall Cavalier; bought this at 82k miles and did all sorts of things that in retrospect might have been over the top; a new cambelt (and cambelt cover) and water pump after purchase in a service totalling around £800, new clutch at ~99k miles which "still had some meat on it" according to the garage even though 1st/reverse were impossible when clutch was hot.. several other comprehensive services and finally some welding work at ~125k (also not cheap, for a car that was by now worth approximately the same as the work being carried out)
HOWEVER despite ALL the work done, ALL the money spent on what is a dog of a car compared to the fine LCR I have the privelege of owning now.. I still deem it worthwhile.. I still own the car (and it still runs at 133k despite hardly any use)! And it only ever broke down on me once when the alternator failed; my mates push-started me and I made it back to the garage at the bottom of the red mark on the fuel gauge
So to sum it up; as I did with my trusty Cavalier; you know the rest of the car, you know its remaining niggles and whether or not the trim rattles, you know all the little fixes to common faults you've carried out that may or may not affect any replacement; at the end of the day you picked a Leon for a reason.. for as long as you like the car, I'd say it's worth keeping it on the road.
Hope this helps
Alex