Our new Fabia doesn’t have cruise control but I am enjoying the similar functionality of the speed limiter. You can set this to your desired speed and then can’t exceed this except by flooring the accelerator or travelling down a steep enough hill to accelerate the car by gravity-assist (in which case an alarm will sound).
I have been finding this a boon as you can give much less attention to not going to fast, freeing it up for the important tasks of paying attention to what is happening on the road (including those all-important speed limit change signs). Because it limits rather than fixes the speed, you can drop down if the traffic ahead slows and, if it slows too much, the set speed is probably going to be enough to overtake safely if it is otherwise safe to do so.
With that tool in hand, the next things to test are whether driving slower than the speed limit on motorways gives a noticeable gain in fuel economy (theoretically sticking to a limit of 60mph should work better although traffic flow will probably also affect this) and seeing how much longer this causes journeys to take (they should be slower but it depends on average speed across the journey – no point speeding up to reach the traffic queue where you have to slow down more drastically).