Weight / Fat loss

^ / ^^ I must be building strength, as am starting to find squats easier (and have been increasing the weight I lift).

That can be technique as much as strength, particularly at the beginning.

I guess it's just that, as I'm not seeing as much visible impact for legs as anything I do for upper body work, the impact feels less obvious if that makes sense.

If you're a typical cyclist then your lower body strength was proportionately significantly better than your upper body strength when you started strength training, so your upper body strength may simply be the easier win at the moment. And the theory is that squats also boost the gains of other lifts, if you're doing them in combination in your programme.

I think upping the weight is the key thing. I'm a mighty 62kg and lifting 52kg with squats. Will start slowly upping it, but keeping reps low, coz, as itsbruce says, it seems high weight / low rep is key for strength

Simple 3x5 or 5x5 programmes work very well until you hit intermediate levels (e.g. squatting about 1.5xbodyweight) or, depending on your build and age, you just hit a plateau where the gains disappear.