As far as I know

1) All VW/Audi/Skoda/Seat 1.4 Petrol NON TSi engines are cam belt

These engines have plastic pulley wheels that are prone to failure - cambelt changes must be 40k/4 years. In my experience they are rather partial to drinking higher octane petrol otherwise you can have piston failures. I still own a now somewhat ageing 1.4 16v Octavia (cam belt) now with 98k miles. Engine running well but has almost always been fed higher octane petrol. When new I was told 110k before cam belt change, I did have the dreaded plastic pulleys staring to fail at 56k but it didn't throw the belt it just made a funny noise - fixed under warranty.

2) All VW/Audi/Skoda/Seat 1.4 Petrol TSi engines are cam chain.

I've heard of problems with the higher powered (Turbo + supercharged) versions especially when chipped. Yet again these are also prone to piston failure. I know a few cars with the lower powered vesion (122-5bhp ) - thus far absolutely superb - powerful especially at lower revs, very quiet and suprisingly economical. One fitted into a 60reg Octavia achieved 52mpg driving to Germany.

>Save yourself some money-dump about 1/4 of your 50:50 coolant mixture and top up with tap >water. This'll reduce the octane requirement of the engine by about 2 points so 95 RON >effectively becomes 97 RON.

How would changing the coolant mix change the octane requirement?

With the Octavia 1.4 16v if you use 95 RON petrol you can detect a slight pinking/tinkling sound on mid/full throttle at lower revs. Fine with higher octane petrol. The car has done this from new - I did take it back to the dealer at the time but was told this was normal for this engine. I've generally used higher octane fuel since.