Labs

I don't know how NatSci is split but from a purely Chemistry aspect:

I barely did any practical work in school/college. A handful of titrations is probably a decent summary.

First year of university - dreaded labs, quite daunting. I felt massively out of my comfort zone. You get a day and some instructions - go forth and chemistry. Problem is, I had no idea what X and Y were equipment-wise so it was all a bit traumatic. Oh, but you learn! The lab reports can be difficult and frustrating, but they are useful. There's far more worth from university practicals than in school. They're actually used to help you learn in university, where as most schools really are just ticking boxes to fulfill the GCSE requirement.

Second year - labs were so much better because I went in there and had this...confidence.

It can be stressful but it's a nice change from sat in lectures. There will be some lecture courses you don't understand and that can be tedious. Actually getting up and 'doing' something during your week is pretty cool. Helps keep the focus a bit. You're nice and busy in the synthetic labs too so the time flies.

Basically, I wouldn't judge labs based on your previous experience. Chemistry is a practical subject so if you want to pursue it in any way then you need to embrace the practical side. I don't think you'll find a purely theoretical course at undergrad either for that sole reason. Physics has some lab aspects from what I gather as well, but I expect they resemble more like the phys chem labs - data collection and analysis sort of stuff rather than synthesis which will be a bigger chunk of chemical labs.

Do whatever you fancy at undergrad and don't worry about the labs until you get there. Specialise with your master's or later if you want to seek solely theoretical. You'll have a solid background from which to judge then.