Modern engines running modern oil really do not benefit from any additives these days. And indeed, there is evidence that they can even do more harm than good.
Also, as you have stated, if you bother to use decent fuels like Shell V-Power, or the new Esso Synergy, they have decent additive packs anyway which do the job of keeping the fuel system, inlet valve stems and combustion chamber nice and clean for you.
Combine that with a sympathetic driving regime like this: After starting, warm the engine gently by driving in a low gear, keeping the load on the engine low whilst it is warming up - and I mean the oil fully warmed, not just the coolant. When the engine is fully warmed right through, don't be scared to give the car a decent caning on wide-open throttle once in a while. Then when you are nearing your destination, drive gently for the last few minutes, then once stationary, allow the engine to idle for a minute before shutting down. Yes, I know that turbo-charged Skoda have an auxiliary water pump which runs coolant round the turbo after shut-down, but to me, this is still best practice as it allows the oil to flow through the turbo as it cools as well.
And you'll have no problems! This regime has served me well for cars and motorbikes, including race engines, over my 35 year driving and racing career! It's all about having just a little mechanical sympathy and using decent fluids.
Hope this helps!