Not sure how helpful I would be and I am sorry for my bad English, I am a Bulgarian. I own a
Leon mk2 with 1.8TSI engine which I think was not available in UK before, so I can share some thoughts. Mine is the first version of the engine which is 160HP. This engine has been created with the idea of having max torque on a broad rev range and it's the first you'll notice when you drive it: it pulls like a rocket regardless of revs and gear and it seems like it is doing it without any effort at all. Furthermore, the engine block is made of grey cast iron which has been chosen for its acoustic properties and also employs twin balancer shafts which all makes it a very quiet engine with no vibrations felt at all. This is personal but I am in love with the fact I am able to effortlessly overtake some roaring cars with no engine roar on my side, as if I am not doing anything special at all. Well, with the new Leon there are some engine noises you can select to be heard from the audio so if you're after roaring engine sound, you can at least use it for your own pleasure inside the car despite it being just a gimmick. There is almost no turbo lag, especially after worm up. Fuel consumption is the same as in specs, not sure how it translates to mpg, I get 10l/100km in city driving and about 7-8 on highway.
However,
Leon mk3 gets the newest version of the engine which has employed some advances on the first 1.8TSI, mainly it gets indirect injection in addition to the direct one, also some other clever improvements which make for
lower consumption and more power like 180HP. I am absolutely convinced the new engine is even greater to drive and I am looking for eventually upgrading my Leon to the mk3 with this newer engine version sooner or later. Btw, the engine uses a timing chain so it doesn't need change and will save you some money.
As a downside, those type of engines are optimized for higher octane fuel and also require low sulfur gasoline, so you should make sure you use a good fuel. In the manual it's stated that it can be driven on 95 but there will be a slight decrease in power output.
I hope that helps and I am sure you've made the right choice with the 1.8TSI. I would chose it day and night over any Diesel engine.