Is that the 1.9 diesel which has appeared in everything from Skoda/VW/FIAT etc..through to Vauxhall and Peugeot vans etc? Certainly a good motor.
Two different engines, same displacement. The FIAT 1.9 was used across FIAT and Opel (Vauxhall) cars (GM and FIAT had a partnership from the mid-1990s up to 2004), plus some Peugeot/Citroën vans which had FIAT twins (e.g., Boxer).
The VW 1.9 was used only within Volkswagen Group brands.
Of the two, the FIAT-developed one is the better engine, using the (then) more advanced common-rail injection system; VW still used single injectors at this point. Both are good for over a quarter of a million miles, but the FIAT engine has better power and torque delivery, and is quieter too. As soon as the patents on common-rail expired, VW ditched the PDI engines and made their own common-rail models. Those common-rail engines were the ones that had the dodgy software that was used to cheat on the emissions tests.
The Fabia isn’t a “Polo in different frock” - it’s the other way around. The good thing about a Polo is that it’s a Fabia with better materials in the cabin. The Fabia we’re talking about is a facelift of the Mk1 Fabia, which was the first car to be released on its platform; the Polo followed 18 months later. Staff at Skoda did a lot of the production engineering on this car before start of production to improve quality, fit and finish and reliability, and then ran it for a year to get the final bugs out. Only then was it spun up at VW and Seat facilities. It’s normal for large companies to have a lead plant on models like this, but Skoda is acknowledged as the quality leader within VW Group.
For fuel economy, approach lights/junctions in high gear with foot off accelerator.. Momentum will drive engine and obviate need for engine to 'scavenge' fuel to keep running.
Modern engines with electronic fuel injection cut off the fuel supply when you apply the brake (without the clutch-pedal depressed).
Engine braking is from an era when the mechanical brakes weren’t very effective, and needed all the help they could get. These days, the brake pedal is the most effective way of stopping the car, especially with ABS ensuring you don’t lose the ability to steer.